Journal articles: 'Orbital structure'

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CHEN, ZHENHUA, JINSHUAI SONG, LINGCHUN SONG, and WEI WU. "A VALENCE BOND APPROACH BASED ON LEWIS STRUCTURES." Journal of Theoretical and Computational Chemistry 07, no. 04 (August 2008): 655–68. http://dx.doi.org/10.1142/s0219633608004039.

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In this paper, a valence bond method based on Lewis structures, called LVB, is presented. The method uses a Slater determinant expansion of doubly occupied orbitals for describing a Lewis structure, where two orbital sets, semi-localized orbitals, called bond orbitals, and localized hybrid atomic orbitals (HAOs), are employed. The levels of LVB method are fashioned as LVBS, LVBSD, etc. LVBS involves only the single bond orbital replacements with HAOs, while LVBSD involves also double replacements, and so on. Tests of three examples, methane, methylene, and benzene, show that the LVB method at both of LVBS and LVBSD levels gives results that match those of the VBSCF method very well, even though the form of LVB wave function is much compact.

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Ghosh, U. S., B. Mukherjee, and S. Rai. "Shell model study of nuclear structure in 63,65,67Ga." International Journal of Modern Physics E 29, no. 07 (July 2020): 2050045. http://dx.doi.org/10.1142/s0218301320500457.

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Shell model calculations have been performed in [Formula: see text] model space using two different interactions viz. jj44bpn and jun45pn to explore nuclear structure in [Formula: see text]Ga. Calculated excitation energies are compared with previously reported experimental values and a good agreement has been observed. Transitions strengths are also calculated using two sets of effective charges for proton and neutron and are compared with nearby [Formula: see text]Zn isotopes. Occupation probabilities of protons and neutrons corresponding to individual orbitals (namely [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] orbital), and dominant particle configurations for individual spin states have been presented as well. Calculations suggest major role of intruder [Formula: see text] orbital in constructing the wave functions of higher angular momentum states, whereas, the lower excited states are mainly dominated by contributions from [Formula: see text] orbitals.

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Baldev, Vibha, and Shailja Tibrewal. "Anomalous orbital structure mimicking fracture of orbital floor." Journal of American Association for Pediatric Ophthalmology and Strabismus 24, no. 3 (June 2020): 175–77. http://dx.doi.org/10.1016/j.jaapos.2020.01.016.

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Hotta, Takashi, Elbio Dagotto, Hiroyasu Koizumi, and Yasutami Takada. "STRIPES IN MANGANITES." International Journal of Modern Physics B 14, no. 29n31 (December 20, 2000): 3494–99. http://dx.doi.org/10.1142/s021797920000399x.

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Topological aspects of the stripe structure in manganese oxides are discussed in terms of the "winding number" w associated with the Berry-phase conncection for e g orbitals acquired by the parallel transport through the periodic array of Jahn-Teller centers. For La 1-x Ca x MnO 3, w is shown to characterize both the three-dimensional spin-charge-orbital structures in the antiferromagnetic phase for x≥1/2 and the charge-orbital stripes in the two-dimensional ferromagnetic phase for <1/2.

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Li, Yu-Qiong, Qian He, Jian-Hua Chen, and Cui-Hua Zhao. "Electronic and chemical structures of pyrite and arsenopyrite." Mineralogical Magazine 79, no. 7 (December 2015): 1779–89. http://dx.doi.org/10.1180/minmag.2015.079.7.05.

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AbstractThe first-principles plane-wave pseudopotential method is used to study the electronic and chemical structures of pyrite (FeS2) and arsenopyrite (FeAsS). The results indicate that an antibonding interaction occurs between Fe and As atoms in arsenopyrite. This interaction results in the Fe atom being repelled towards the S atom to stabilize antibonding orbitals, causing a larger S–Fe–S angle in arsenopyrite than in pyrite and a distortion in the arsenopyrite structure. In arsenopyrite, Fe–Fe distances are alternately long and short. The low spin density of the Fe d electrons supports this configuration in arsenopyrite. However, electron density calculations indicate that there is negligible electron density present between Fe atoms. This result indicates that cation-anion interactions are dominant in arsenopyrite. The pyrite Fe 3d orbital is split below the Fermi level, whereas the arsenopyrite Fe 3d orbital is not split, which can be attributed to the stronger interatomic bonding effects between Fe and S atoms in pyrite compared to arsenopyrite. It is found that the d-p orbital interactions between Fe and S atoms lead to bonding-antibonding splitting in both pyrite and arsenopyrite. However, the bonding effects between pyrite Fe and S atoms are stronger than in arsenopyrite. In arsenopyrite, the bonding interaction between the As 4p and Fe 3d orbitals is very weak, while the antibonding effect is very strong. The p-p orbital interaction is the dominant effect in As–S bonding. Frontier orbital calculations indicate that the Fermi levels of pyrite and arsenopyrite are notably close to each other, resulting in similar electrochemical activities. Orbital coefficient results show that the pyrite Fe 3d and S 3p orbitals are the active orbitals in the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), respectively. In the case of arsenopyrite, Fe 3d orbitals are very active in both the HOMO and LUMO. Moreover, the activity of the As 4p in the HOMO is greater than S 3p, whereas the opposite situation occurs in the LUMO. Based on these results, As atoms could be one of the active sites for the oxidation of arsenopyrite. In addition, separation of arsenopyrite and pyrite could be achieved by utilizing the difference in chemical reactivities of iron in the two minerals.

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Masan, Samuel E. P. P., Fitri N. Febriana, Andi H. Zaidan, Ira Puspitasari, and Febdian Rusydi. "Evaluation of the Electronic Structure Resulting from ab-initio Calculations on Simple Molecules Using the Molecular Orbital Theory." Jurnal Penelitian Pendidikan IPA 7, no. 1 (January 28, 2021): 107. http://dx.doi.org/10.29303/jppipa.v7i1.545.

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Hartree Fock (HF) and Density Functional Theory (DFT) have been commonly used to model chemical problems. This study uses the Molecular Orbital Theory (MOT) to evaluate the electronic structure of five diatomic molecules generated by HF and DFT calculations. The evaluation provides an explanation of how the orbitals of a molecule come to be and how this affects the calculation of the physical quantities of the molecule. The evaluation is obtained after comparing the orbital wave functions calculated by MOT, HF, and DFT. This study found that the nature of the Highest Occupied Molecular Orbital (HOMO) of a molecule is determined by the valence orbital properties of the constituent atoms. This HOMO property greatly influences the precision of calculating the molecular electric dipole moment. This shows the importance of understanding the orbital properties of a molecule formed from the HF and DFT calculations

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Bryar, Traci R., and Donald R. Eaton. "Electronic configuration and structure of paramagnetic iron dinitrosyl complexes." Canadian Journal of Chemistry 70, no. 7 (July 1, 1992): 1917–26. http://dx.doi.org/10.1139/v92-240.

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The electronic and geometric structures of paramagnetic iron dinitrosyl complexes have been investigated using electron spin resonance, infrared spectroscopy, and X-ray crystallography. It is concluded that these compounds are best described as 17 electron complexes with a d9 configuration rather than the d7 configuration assumed by most previous investigators. The anisotropy of the g values, determined from the electron spin resonance spectra of frozen solutions, varies considerably from complex to complex. The results are consistent with the supposition that all of the complexes have a distorted tetrahedral geometry, but the nature of the distortion changes as the ligands are varied. As a result of this variation there are changes in the nature of the spin-containing d orbital. Ligands containing hard, nonpolarizable donor atoms such as oxygen or fluorine produce a distortion towards a planar geometry, placing the odd electron in a predominantly [Formula: see text] orbital, while those containing softer donor atoms such as phosphorus or sulfur give complexes with a different type of distortion, leading to placement of the odd electron in a predominantly [Formula: see text] orbital. Nitrogen and halide donor ligands produce smaller distortions, leading to spin-containing molecular orbitals with contributions from a mixture of d orbitals. In accordance with this model, the crystal structure of [Fe(NO)2I2]− has been found to be only slightly distorted from regular tetrahedral coordination about the iron atom.

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Cargnoni, Fausto, Simone Cenedese, Paolo Ghigna, Mario Italo Trioni, and Marco Scavini. "Electronic Structure and Magnetic Coupling of Pure and Mg-Doped KCuF3." Advances in Condensed Matter Physics 2018 (August 15, 2018): 1–10. http://dx.doi.org/10.1155/2018/9164270.

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We investigated the electronic and magnetic properties of KCuF3 and KCu0.875Mg0.125F3 crystals by means of Density Functional periodic computations at the B3LYP level of theory. We considered four possible magnetic ordering of the unpaired electrons on copper ions. Both materials are correctly predicted as being 1D antiferromagnetic insulators, and the superexchange parameters in the crystallographic ab planes and along the c direction measure +10 and -600 K, respectively. Residual spin polarization is found also on fluorine atoms, in agreement with literature results. We found a complete orbital ordering at Cu sites: in the copper reference frame dxy, dyz, dxz, and dz2 orbitals contain about 2 electrons each, while the dx2-y2 orbital is only partially filled. The perturbation induced by doping of KCuF3 with Mg is very strong and localized on the first shell of F neighbours. Mg has a very small influence on the ordering of the 3d orbitals of copper and on the Cu-Cu magnetic superexchange parameters but reduces significantly the absolute energy differences between the antiferromagnetic ground state and the ferromagnetic phase, in agreement with the experiment. The absence of long range effects makes Mg a suitable dopant for the investigation of strongly correlated electronic systems by means of orbital dilution.

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Guimon, C., G. Pfister-Guillouzo, D. Ilavsky, M. Marchalin, and A. Martvon. "Structure électronique et réactivité des pyridyl-isothiocyanates. Étude quantique et photoélectronique." Canadian Journal of Chemistry 64, no. 8 (August 1, 1986): 1467–73. http://dx.doi.org/10.1139/v86-242.

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On the basis of molecular orbital calculations made in association with ultraviolet photoélectron spectroscopy (ups), it is demonstrated that the regioselectivity of the cycloadditions of pyridyl-2-isothiocyanate with 1,3-dipoles is directed by frontier orbitals. The different cycloadditions (4 + 2, 2 + 3, 2 + 2) vary with the overlap of these orbitals and this shows the importance of secondary interactions, namely the localization of the orbitals on the atoms adjacent to the bonds that are formed during the addition.

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10

Purton, J., and D. S. Urch. "High-resolution silicon Kβ X-ray spectra and crystal structure." Mineralogical Magazine 53, no. 370 (April 1989): 239–44. http://dx.doi.org/10.1180/minmag.1989.053.370.11.

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AbstractHigh-resolution X-ray emission spectra (XES) are presented for minerals with a variety of structures. The participation of the Si 3p orbitals in bonding is influenced by the local structure around the silicon atom. In orthosilicates the distortion of the SiO44--tetrahedron influences both peak-width and the intensity of the high-energy shoulder of the Si-Kβ spectrum. In minerals containing Si-O-Si bonds there is mixing of the Si 3s and 3p orbitals giving rise to a peak on the low-energy side of the main Si-Kβ peak. When combined with X-ray photoelectron spectra (XPS), a complete molecular orbital picture of bonding can be established.

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11

van de Ven, Glenn, Ellen Verolme, Michele Cappellari, and Tim de Zeeuw. "Orbital structure of triaxial galaxies." Symposium - International Astronomical Union 220 (2004): 179–80. http://dx.doi.org/10.1017/s0074180900183159.

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We have developed a method to construct realistic triaxial dynamical models for elliptical galaxies, allowing us to derive best-fitting parameters, such as the mass-to-light ratio and the black hole mass, and to study the orbital structure. We use triaxial theoretical Abel models to investigate the robustness of the method.

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12

Voglis, N., M. Harsoula, and G. Contopoulos. "Orbital structure in barred galaxies." Monthly Notices of the Royal Astronomical Society 381, no. 2 (September 28, 2007): 757–70. http://dx.doi.org/10.1111/j.1365-2966.2007.12263.x.

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13

GALVAN, DONALD H. "ELECTRONIC STRUCTURE CALCULATIONS FOR MoSe2 USING EXTENDED HUCKEL TIGHT-BINDING METHOD." Modern Physics Letters B 18, no. 01 (January 10, 2004): 35–44. http://dx.doi.org/10.1142/s0217984904006561.

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To gain insight into the electronic properties of MoSe 2 (molybdenum selenide, also known as drysdallite), electronic structure calculations, total and projected density of states, crystal orbital overlap population and Mulliken population analysis were performed. The calculated energy bands depict a semiconductor behavior with a direct gap (at K) of 0.91 eV and an indirect gap (from Γ to K) of 3.6 eV, respectively. Total and projected density of states provided information about the contribution from each orbital of each atom to the total density of states. Moreover, the bonding strength between some atoms within the unit cell was obtained. Mulliken population analysis corroborates the electron filling of the Mo dz2 orbitals in agreement with another experimental and theoretical results.

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14

Qi, Yi, and Anton de Ruiter. "Phase structure of co-orbital motion with Jupiter." Monthly Notices of the Royal Astronomical Society 494, no. 4 (April 22, 2020): 4695–705. http://dx.doi.org/10.1093/mnras/staa1069.

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ABSTRACT In this paper, we investigate the dynamics of the inclined co-orbital motion with Jupiter through a torus phase structure in the Sun–Jupiter circular restricted three-body problem. A semi-analytical method to establish the Hamiltonian approximation for the inclined co-orbital motion is proposed. Phase structures of different kinds of co-orbital behaviours are shown in the torus space clearly. Based on numerical computation, we analyse the evolution and the connection of different co-orbital dynamics. Summarizing results and conclusions in this paper, we find two main principles throughout the investigation of the co-orbital motion: (i) the libration amplitude of the resonant angle for the co-orbital motion is bounded by the corresponding Hamiltonian isosurface in the torus space and (ii) the co-orbital behaviour is influenced by collision curves, and with the decrease of the Hamiltonian value, the influence is more significant.

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15

Shen, Wanting, Lihong Han, Dan Liang, Chunfang Zhang, Quhe Ruge, Shumin Wang, and Pengfei Lu. "Structural, stability, and vibrational properties of BinPm clusters." International Journal of Modern Physics B 32, no. 10 (April 13, 2018): 1850117. http://dx.doi.org/10.1142/s0217979218501175.

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An in-depth investigation is performed on stability mechanisms, electronic and optical properties of III–V semiconductor vapor phases clusters. First principles electronic structure calculations of CAM-B3LYP are performed on neutral Bi[Formula: see text]P[Formula: see text] (n + m [Formula: see text] 14) clusters. The geometrical evolution of all stable structures remains amorphous as the clusters size increases. Binding energies (BEs), energy gains and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps confirm that all four-atom structures of Bi[Formula: see text]P[Formula: see text] clusters have more stable optical properties. Orbitals composition and vibrational spectra of stable clusters are analyzed. Our calculations will contribute to the study of diluted bismuth alloys and compounds.

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GESARI, S. B., M. E. PRONSATO, and A. JUAN. "GRAIN BOUNDARY SEGREGATION OF HYDROGEN IN BCC IRON: ELECTRONIC STRUCTURE." Surface Review and Letters 09, no. 03n04 (June 2002): 1437–42. http://dx.doi.org/10.1142/s0218625x02003998.

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The electronic properties of H impurity in an Fe Σ = 5, 53.1° [100] (012) symmetrical tilt grain boundary (GB) were studied using qualitative electronic structure calculations in the framework of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. A large cluster containing 197 Fe atoms was used to simulate the local environment of the boundary. The most stable positions for one H atom and two H atoms at the GB core were determined. The total energy of the cluster decreases when the H atoms are at that location, making it a possible site for H accumulation. The binding energy found was less than that of a Σ = 5 [100] (013) GB. An analysis of the orbital interaction reveals that H–Fe bonding involves mainly the Fe 4s and H 1s orbitals. A higher contribution of d orbitals is present, which show a different behavior when compared with mixed dislocation and vacancy in the bulk Fe. The interatomic bonding along the Fe atom chains via H atoms is very inefficient, thus resulting in significant weakening of the interatomic bonding. H–H interaction was also analyzed.

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Boudon, Alain, Jan Szymoniak, Jacques R. Chrétien, and Jacques-Emile Dubois. "Modelling the binding step in dopamine receptor–antagonist interactions." Canadian Journal of Chemistry 66, no. 12 (December 1, 1988): 2995–3002. http://dx.doi.org/10.1139/v88-465.

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Modelling of the binding step in dopamine receptor–antagonist interactions was undertaken using sixteen antagonists belonging to the following five chemical series: phenothiazines, thioxanthenes, butyrophenones, benzamides, and benzisoxazoles. The Lower Unoccupied Molecular Orbitals (LUMOs) of the antagonists used for these interactions were compared using a similarity τij index, which enabled us to define the characteristic orbital forms of the active molecules. The result of the intersection of these representative orbital forms was the form common to the antagonists' LUMOs. This form corresponds to the orbital form of the indole's Higher Occupied Molecular Orbital (HOMO), and thus suggests that the aromatic binding site of the dopamine receptor is part of a tryptophan type structure.

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Gudim, M. S., O. M. Goncharuk, and A. A. Oblyvach. "The structure and clinical features of cranio-orbital and orbital tumors with different histological structure." INTERNATIONAL NEUROLOGICAL JOURNAL, no. 2.88 (May 16, 2017): 16–22. http://dx.doi.org/10.22141/2224-0713.2.88.2017.100193.

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19

Yang, Ming, and Rui-Ning Wang. "Topological insulator in tellurium-based perovskites." International Journal of Modern Physics B 29, no. 12 (May 10, 2015): 1550073. http://dx.doi.org/10.1142/s0217979215500733.

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Perovskites have a cubic structure with general formula of ABO 3. The meritorious features such as colossal magnetoresistance, ferroelectricity, superconductivity and charge ordering are observed in this class of materials and make perovskites a hot-spot which receive considerable research interest in recent years. Here, we predict a new topological insulator in tellurium-based perovskites and calculate its band structures, electronic density of states (DOS) and Z2 quantum number. By orbital-projected band structure analysis we find that the orbitals involved in the topological band-inversion process are s- and p-orbitals. The topological surface state is also given. This new material can provide dissipationless signal current for devices and is expected to be applied in spintronics devices.

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Li, Xiao-Hong, Rui-Zhou Zhang, and Xian-Zhou Zhang. "Theoretical investigation of some N-nitrosodiphenylamine biological molecules — A natural bond orbital (NBO) study." Canadian Journal of Chemistry 89, no. 10 (October 2011): 1230–35. http://dx.doi.org/10.1139/v11-084.

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Theoretical study of several N-nitrosodiphenylamine biological molecules has been performed using quantum computational ab initio RHF and density functional B3LYP and B3PW91 methods with 6–311G++(d,p) basis set. Geometries obtained from density functional theory (DFT) calculations were used to perform Natural bond orbital (NBO) analysis. The p characters of two nitrogen natural hybrid orbitals (NHOs) σN3−N2 increase with increasing σp values of the substituents on the benzene, which results in a lengthening of the N3–N2 bond. The p characters of oxygen NHO σO1−N2 and nitrogen NHO σO1−N2 bond orbitals decrease with increasing σp values of the substituents on the benzene, which results in a shortening of the N2=O1 bond. It is also noted that decreased occupancy of the localized σN3−N2 orbital in the idealized Lewis structure, or increased occupancy of [Formula: see text]of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are also related to the resulting p character of the corresponding nitrogen NHO of σN3−N2 bond orbital.

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21

Duffy, Jonathan. "Spin-resolved momentum densities: probing orbitals in magnetic oxides." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1554. http://dx.doi.org/10.1107/s2053273314084459.

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Studies of spin-resolved electron momentum densities involve the measurement of the so-called magnetic Compton profile. This is a one-dimensional projection of the electron momentum distribution of only those electrons that contribute to the spin moment of a sample. The technique is applicable to ferri- and ferromagnetic materials. Since electrons originating from different atomic orbitals have specific momentum densities, it is often possible to determine the origin of the magnetism present. Typically, interpretation requires the use of electronic structure calculations using molecular orbital and band structure approaches. The profile is obtained experimentally via the inelastic "Compton" scattering of high energy X-rays. For the experiments discussed here, the high energy beamlines at the ESRF and SPring-8 synchrotron X-ray sources were used, where we have a cryomagnet which can provide a sample environment with applied magnetic fields up to 9 Tesla, at temperatures from 1.3K to 600K. In this talk, we discuss our combined experimental and theoretical study of the spin density of the low-dimensional frustrated metamagnet Ca3Co2O6. The spin moment, measured using magnetic Compton scattering, confirms the existence of a large unquenched Co orbital moment (1.310.1 μB). With regards to the orbital occupation, we have performed molecular orbital calculations on the active trigonal CoO6cluster in order to determine which Co 3d orbitals are responsible for the observed electronic and magnetic behaviour and the observed orbital moment, and revealing the existence a oxygen spin moment of approximately 0.9 μB. Electronic structure calculations with a Hubbard U energy term give Compton profiles which are in good agreement with our experimental data. The magnetic Compton profile exhibits oscillations, which are well described, and their frequency in momentum space corresponds to the real-space inter-cobalt site bond length.

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Pradhan, Manas Ranjan, and E. G. Rajan. "Orbital Structure Analysis in Molecular Electronics." International Journal of Computer Applications 4, no. 8 (August 10, 2010): 35–43. http://dx.doi.org/10.5120/846-1181.

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23

Lees, Joanna F., and M. Schwarzschild. "The orbital structure of galactic halos." Astrophysical Journal 384 (January 1992): 491. http://dx.doi.org/10.1086/170891.

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Terzic, B., and H. E. Kandrup. "Orbital structure in oscillating galactic potentials." Monthly Notices of the Royal Astronomical Society 347, no. 3 (January 21, 2004): 957–67. http://dx.doi.org/10.1111/j.1365-2966.2004.07256.x.

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Itagaki, Naoyuki, Kiyomi Ikeda, and Shigeto Okabe. "Molecular-Orbital Structure in Be Isotopes." Acta Physica Hungarica 13, no. 1-3 (2001): 153–56. http://dx.doi.org/10.1556/aph.13.2001.1-3.18.

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Neupane, H. K., and N. P. Adhikari. "Structural, Electronic and Magnetic Properties of Impurities Defected Graphene/MoS2 Van Der Waals Heterostructure: First-principles Study." Journal of Nepal Physical Society 7, no. 2 (June 30, 2021): 1–8. http://dx.doi.org/10.3126/jnphyssoc.v7i2.38578.

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Two-dimensional (2D) pristine and defected van der Waals (vdW) heterostructure (HS) materials open up fortune in nanoelectronic and optoelectronic devices. So, they are compatible for designing in the fields of device applications. In the present work, we studied structural, electronic and magnetic properties of vdW (HS) graphene/MoS2 ((HS)G/MoS2), Nb impurity defect in vdW (HS) graphene/MoS2 (Nb-(HS)G/MoS2), and Tc impurity defect in vdW (HS) graphene/MoS2 (Tc-(HS)G/MoS2) materials by using spin-polarized DFT-D2 method. We examined the structure of these materials, and found that they are stable. Based on band structure analysis, we found that (HS)G/MoS2, Nb-(HS)G/MoS2 and Tc-(HS)G/MoS2 have metallic characteristics. Also, (HS)G/MoS2 and Tc-(HS)G/MoS2 materials have n-type Schottky contact, while Nb-(HS)G/MoS2 material has p-type Schottky contact. To understand the magnetic properties of materials, we have used DoS, IDoS and PDoS calculations. We found that (HS)G/MoS2 is a non-magnetic material, but Nb-(HS)G/MoS2 and Tc-(HS)G/MoS2 are magnetic materials. Magnetic moment of Nb-(HS)G/MoS2 and Tc-(HS)G/MoS2 materials are -0.24 μB/cell and +0.07μB/cell values respectively from DoS/PDoS calculations, and 0.26 μB/cell and 0.08μB/cell values respectively from IDoS calculations. Up-spin and down-spin states of electrons in 2p orbital of C atoms, 3p orbital of S atoms, 4d orbital of Mo atoms, 4d orbital of Tc atom in Tc-(HS)G/MoS2, and 2p orbital of C atoms, 3p orbital of S atoms, 4p & 4d orbitals of Mo atoms, 4p & 4d orbitals of Nb atom in Nb-(HS)G/MoS2 have major contribution for the development of magnetic moment.

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Mishra, K. C., I. Osterloh, H. Anton, B. Hannebauer, P. C. Schmidt, and K. H. Johnson. "Electronic Structures and Host Excitation of LaPO4, La2O3, and AlPO4." Journal of Materials Research 12, no. 8 (August 1997): 2183–90. http://dx.doi.org/10.1557/jmr.1997.0292.

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We report the electronic structures and associated optical properties of three inorganic oxides, namely lanthanum oxide, aluminum phosphate, and lanthanum phosphate, calculated by the first principles augmented spherical wave (ASW) and full potential linear muffin tin orbital (FP-LMTO) band structure methods, and the self-consistent field Xα scattered wave (Xα SW) molecular orbital cluster approach. Our calculations indicate negligible effect of the choice of exchange correlation potentials on the position, shape, and relative ordering of the energy bands. The ASW energy gaps in lanthanum phosphate and aluminum phosphate agree satisfactorily with the measured values. A comparison of the electronic density of states for an isolated phosphate group from molecular orbital calculation and that of the valance band from the band structure methods indicates that the nature of bonding within the phosphate groups does not change in aluminum and lanthanum phosphates. The states near the top of the valence band and bottom of the conduction band are mostly due to the phosphate bonding and antibonding orbitals, indicating that optical absorption near the band edge involves excitation of electrons from the bonding levels to antibonding levels associated with phosphate groups. This explains why the optical gaps in many rare earth phosphates are nearly equal.

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BELAYADI, A., B. BOURAHLA, and F. MEKIDECHE-CHAFA. "LOCALIZED ELECTRONIC SURFACE STATES IN METALLIC STRUCTURES." Surface Review and Letters 25, no. 05 (July 2018): 1850101. http://dx.doi.org/10.1142/s0218625x18501019.

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We present theoretical models to study the localized electronic surface states in metallic structures. The materials under study have been chosen with different types of cubic meshes, fcc, sc and bcc. The calculation method used is closely related to the Linear Combination of Atomic Orbitals (LCAO) in the tight-binding method. We consider three cases: each of the atoms is described by a single atomic orbital of [Formula: see text]-, [Formula: see text]- and [Formula: see text]-type orbitals. In order to solve the rectangular secular equations of the systems under study, the phase field matching method is involved. In particular, we apply our approach to calculate the localized electronic surface states of some metals: (i) Chromium and Silver having, respectively, bcc and fcc structure and described as [Formula: see text]-type orbital. (ii) Nickel with sc crystallization and described by [Formula: see text]-type orbital. (iii) Palladium (Pd) given in fcc crystallization and described by [Formula: see text]-type orbital. The obtained results illustrate spatial edge effects between the bulk modes and the localized electronic states of the metallic surfaces over the three orientations of high symmetry path. We observe many localized states above and below the bulk band range. In addition, the relaxation effect on the surface layer has been investigated to compute the localized electronic surface state in this case and illustrate the lift of the degeneracy compared to the first calculations based on an ordered surface. The spacing geometry caused by the relaxation on the surface has been determined by using the Molecular dynamic algorithm and Morse interatomic potential.

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Beylkin, G., and T. S. Haut. "Nonlinear approximations for electronic structure calculations." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 469, no. 2158 (October 8, 2013): 20130231. http://dx.doi.org/10.1098/rspa.2013.0231.

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We present a new method for electronic structure calculations based on novel algorithms for nonlinear approximations. We maintain a functional form for the spatial orbitals as a linear combination of products of decaying exponentials and spherical harmonics centred at the nuclear cusps. Although such representations bare some resemblance to the classical Slater-type orbitals, the complex-valued exponents in the representations are dynamically optimized via recently developed algorithms, yielding highly accurate solutions with guaranteed error bounds. These new algorithms make dynamic optimization an effective way to combine the efficiency of Slater-type orbitals with the adaptivity of modern multi-resolution methods. We develop numerical calculus suitable for electronic structure calculations. For any spatial orbital in this functional form, we represent its product with the Coulomb potential, its convolution with the Poisson kernel, etc., in the same functional form with optimized parameters. Algorithms for this purpose scale linearly in the number of nuclei. We compute electronic structure by casting the relevant equations in an integral form and solving for the spatial orbitals via iteration. As an example, for several diatomic molecules we solve the Hartree–Fock equations with speeds competitive to those of multi-resolution methods and achieve high accuracy using a small number of parameters.

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30

Wang, Songsong, Changliang Han, Liuqi Ye, Guiling Zhang, Yangyang Hu, Weiqi Li, and Yongyuan Jiang. "Electronic Properties of Triangle Molybdenum Disulfide (MoS2) Clusters with Different Sizes and Edges." Molecules 26, no. 4 (February 22, 2021): 1157. http://dx.doi.org/10.3390/molecules26041157.

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The electronic structures and transition properties of three types of triangle MoS2 clusters, A (Mo edge passivated with two S atoms), B (Mo edge passivated with one S atom), and C (S edge) have been explored using quantum chemistry methods. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of B and C is larger than that of A, due to the absence of the dangling of edge S atoms. The frontier orbitals (FMOs) of A can be divided into two categories, edge states from S3p at the edge and hybrid states of Mo4d and S3p covering the whole cluster. Due to edge/corner states appearing in the FMOs of triangle MoS2 clusters, their absorption spectra show unique characteristics along with the edge structure and size.

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31

Ji, Xiangdong, and Yong Zhao. "The Spin Structure of the Nucleon." International Journal of Modern Physics: Conference Series 40 (January 2016): 1660001. http://dx.doi.org/10.1142/s2010194516600016.

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We justify the physical meaning of the spin and orbital angular momentum of free partons in the infinite momentum frame, and discuss the relationship between the Jaffe-Manohar and Ji’s sum rules for proton spin. The parton orbital angular momentum in the Jaffe-Manohar sum rule can be measured through twist-three GPD’s in hard scattering processes such as deeply virtual Compton scattering. Furthermore, we propose that the paton orbital angular momentum as well as the gluon helicity can be calculated in lattice QCD through a large momentum effective theory approach, and provide all the one-loop matching conditions for the proton spin content in perturbative QCD.

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32

Jotani, Mukesh M. "Crystal Structure Optimization and Semi-Empirical Quantum Chemical Calculations of Fused Bicyclic Heterocycles." Advanced Materials Research 1087 (February 2015): 59–63. http://dx.doi.org/10.4028/www.scientific.net/amr.1087.59.

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The crystal structures of two fused pyridine derivatives viz Ethyl 3-amino-6-phenyl-4-tolylfuro[2,3-b]pyridine-2-carboxylate (I) and Ethyl 3-amino-6-phenyl-4-tolylthieno[2,3-b] pyridine-2-carboxylate (II) were optimized by semi-empirical methods using MOPAC2009 program. The geometries optimized for both the structures from Austin Model 1 (AM1) and Parametrization Model 6 (PM6) describe the conformational discrepancy and crystal packing effects. The parametric molecular electrostatic potential (PMEP) calculated by AM1 semi-empirical method describe the involvement of nitrogen and oxygen atoms in the crystal packing interactions in both the structures. The frontier molecular orbitals highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicate the intramolecular charge transfer interactions. The HOMED indices computed for the phenyl rings in the structures describe the p-electron delocalization. The linear regression analysis shows good correlation between experimental and theoretical structures.

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33

Subramaniyan, Vasudevan, Ashok Kumar, Anbarasu Govindaraj, and Ganesan Mani. "Crystal structure and DFT analyses of a pentacoordinated PCP pincer nickel(II) complex." Acta Crystallographica Section C Structural Chemistry 75, no. 6 (May 21, 2019): 734–39. http://dx.doi.org/10.1107/s2053229619006211.

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The reaction of NiCl2 with 1,3-bis[(diphenylphosphanyl)methyl]hexahydropyrimidine in the presence of 2,6-dimethylphenyl isocyanide and KPF6 afforded a new pentacoordinated PCP pincer NiII complex, namely {1,3-bis[(diphenylphosphanyl)methyl]hexahydropyrimidin-2-yl-κN 2}(2,6-dimethylphenyl isocyanide-κC)nickel(II) hexafluoridophosphate 0.70-hydrate, [Ni(C9H9N)(C30H30ClN2P2)]PF6·0.7H2O or [NiCl{C(NCH2PPh2)2(CH2)3-κ3 P,C,P′}(Xylyl-NC)]PF6·0.7H2O, in very good yield. Its X-ray structure showed a distorted square-pyramidal geometry and the compound does not undergo dissociation in solution, as shown by variable-temperature NMR and UV–Vis studies. Density functional theory (DFT) calculations provided an insight into the bonding; the nickel dsp 2-hybridized orbitals form the basal plane and the nearly pure p orbital forms the axial bond. This is consistent with the NBO (natural bond orbital) analysis of analogous nickel(II) complexes.

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34

Sugimoto, Akira, Keisuke Matsumoto, Hideyuki Maruyama, Kazuhiko Mizuno, and Kaku Uehara. "Thermally Unstable 5-(9-Anthrylmethyl)-10-methyl-5,10-dihydrophenazine." Journal of Chemical Research 23, no. 2 (February 1999): 72–73. http://dx.doi.org/10.1177/174751989902300203.

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The title compound in refluxing toluene decomposed to 9-anthrylmethyl derivatives and phenazine as major products upon cleavage of the N–CH2 bond; the orbital interaction of which with π-orbitals of the aromatic ring was suggested by the X-ray crystal structure analysis.

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35

Zhou, Qing Xiao, Zhi Bing Fu, Chao Yang Wang, Xi Yang, Lei Yuan, and Yong Jian Tang. "Electronic and Magnetic Properties of Rare-Earth Atoms Absorbed on Graphene Sheet: A Theoretical Study." Key Engineering Materials 645-646 (May 2015): 40–44. http://dx.doi.org/10.4028/www.scientific.net/kem.645-646.40.

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The electronic and magnetic properties of graphene functionalized by 4f-orbital RE-metal atoms (Ce, Nd, Sm and Eu) were investigated by the density functional theory (DFT) calculations. The results of binding energy and geometry parameters showed that the hollow site, the center of a carbon hexagon, was the most stable adsorption structure. Furthermore, the PDOS results suggested that the electronic hybridization between the RE-adatoms and C atoms was mainly contributed by the 5d orbitals, whereas the 4f-orbital of the metal adatoms dominated the net magnetic moments of the systems significantly.

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36

Yan, Zhi Guo, Tong Jun Zhu, Ai Guo Xuan, and Yuan Xin Wu. "First Principle Study on Mn-Doped Ceria with Different Doping Concentration." Advanced Materials Research 712-715 (June 2013): 541–45. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.541.

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First-principle software bundle based on the density functional theory (DFT) is used to investigate pure CeOB2B and Mn-doped CeOB2B with different doping concentration. The structural model of CeOB2B crystal is constructed and geometrically optimized, the electron density of states and band structure calculated. The results are as follows: the valence band top of CeOB2B is made up with O2p and Ce5d states, and the existence of 4f unoccupied molecular orbital of CeOB2B facilitates the electronic storage. The theoretical calculation models of Mn-doped CeOB2B with different concentration are constructed and calculated, including 2*1*1, 2*2*1 and 2*2*2 supercell models. After CeOB2B is doped, hybridization happens between 4s orbitals of Mn atoms and 2p orbital of O atoms, resulting in 4s orbitals of Mn atoms lose electrons.Moreover, Mn atom is electron donor and O atoms is the electron acceptor. As the doping concentration decreases, the formation energy also decreases.And a smaller formation energy leads to a more stable structure.

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37

Gardella, Joseph A., Susan A. Ferguson, and Roland L. Chin. "π* ← π Shakeup Satellites for the Analysis of Structure and Bonding in Aromatic Polymers by X-Ray Photoelectron Spectroscopy." Applied Spectroscopy 40, no. 2 (February 1986): 224–32. http://dx.doi.org/10.1366/0003702864509565.

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The applications of ESCA to polymer surface analysis include the use of the secondary final-state effects which lead to satellite structure near the core-level photoemission (PE) lines. Specifically, unsaturated and aromatic functionalities in organic compounds and polymers lead to π* ← π shakeup peaks of less than 10 eV lower kinetic energy (higher binding energy). In the surface analysis of polymers, these features can be utilized for qualitative analysis, identification of the presence and structure of aromatic bonding, and quantitative analysis in determining the amount of a particular block or the aromatic containing function in the near-surface region. Carbon Is shakeups are most often used, but the present study includes detailed qualitative and quantitative analysis of shakeup structures from PE lines from each type of atom in hydrocarbon-, siloxane-, and sulfur-containing polymers. These results show the importance of including the shakeup intensity in quantitative peak area calculations and in peak fitting of complex PE envelopes. These studies prove in a variety of systems that the effects of third-row atoms on the final state lead to the presence of shakeup features in atoms with orbitals which do not participate in the aromatic orbital initial state, thus complicating interpretation of structure from the presence of these features. Results from the siloxane and sulfone polymers indicate that previously held assumptions about the nature of the initial-state molecular orbital may overlook the contribution of empty 3d orbitals or increased charge density on the Si or S atom which would spread the pi orbitals to the oxygen in the aromatic siloxane or sulfone systems. Finally, analysis of these features can provide quantitative analysis of polymeric surface structure by monitoring the relative intensity of the feature to the main PE line.

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38

Parajuli, D., G. C. Kaphle, and K. Samatha. "First-Principles Study of Electronic and Magnetic Properties of Anatase and its Role in Anatase-Mxene Nanocomposite." Journal of Nepal Physical Society 5, no. 1 (December 29, 2019): 42–53. http://dx.doi.org/10.3126/jnphyssoc.v5i1.26940.

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The electronic and magnetic properties of Titanium and one of its oxide Anatase are calculated by using Tight Binding Linear Muffin-Tin Orbital Atomic Sphere Approximation (TB-LMTO-ASA) method under Density Functional Theory (DFT). The lattice parameter, band structure, Density of States (DOS) and charge density distributions of Ti and TiO2 (Anatase) required for electronic structure are calculated respectively. The orbital contribution is analyzed by fat band structure; the d- orbital on conduction band and, s and p orbitals on valance bands. Consequently, their magnetic properties are checked. From our study, we found that the magnetic moments of Ti and TiO2 are found to be 2.2 μB and 0 respectively. The total Density of States for spin up and down electron have smaller difference in Ti and symmetric in TiO2 indicates that Ti slightly paramagnetic and Anatase is non magnetic in nature. The charge density plots reveals the concentration of electrons at the site under study. Anatase can be deposited onto Mxene to form Mxene-Anatase nanocomposite which has several excellent applications in the field of biosensors, biocompatible materials, energy storage devices, topological insulators etc.

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39

JAYA, S. MATHI, R. JAGADISH, R. S. RAO, and R. ASOKAMANI. "ELECTRONIC STRUCTURE OF THE PEROVSKITE OXIDES SrCrO3 AND PbCrO3." Modern Physics Letters B 06, no. 02 (January 20, 1992): 103–12. http://dx.doi.org/10.1142/s0217984992000132.

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The electronic structure calculations of the perovskite oxides SrCrO 3 and PbCrO 3 performed both in the paramagnetic and antiferromagnetic phases are reported here. The calculations were carried out using the Linear Muffin Tin Orbital method within the Atomic Sphere Approximation. The quantitative results obtained are found to give a good description of the electronic states of SrCrO 3 and are in agreement with the Goodenough’s qualitative chemical picture. However, it is not able to predict the semiconducting gap in PbCrO 3 which is an antiferromagnetic semiconductor. But the value of the theoretically calculated magnetic moment at the Cr site in PbCrO 3 is found to be in good agreement with the experimentally observed value. The calculations show strong hybridisation between the Cr -3d and O -2p orbitals and the density of states at the Fermi energy has major contributions from these hybridised orbitals.

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40

Poon, M. Y., and D. Merritt. "Orbital Structure of Triaxial Black Hole Nuclei." Astrophysical Journal 549, no. 1 (March 2001): 192–204. http://dx.doi.org/10.1086/319060.

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41

Kirk, W. A., and Naseer Shahzad. "Normal structure and orbital fixed point conditions." Journal of Mathematical Analysis and Applications 463, no. 2 (July 2018): 461–76. http://dx.doi.org/10.1016/j.jmaa.2018.02.022.

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42

Larsson, Sven, and J. Mauricio O. Matos. "Electron transfer rate and molecular orbital structure." Journal of Molecular Structure: THEOCHEM 120 (February 1985): 35–40. http://dx.doi.org/10.1016/0166-1280(85)85090-9.

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43

Leroy, G., and D. Peeters. "The localized orbital approach to molecular structure." Journal of Molecular Structure: THEOCHEM 169 (August 1988): 257–71. http://dx.doi.org/10.1016/0166-1280(88)80264-1.

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44

Horner, M. Glenn, and James R. Larson. "A molecular orbital study of exciplex structure." Journal of Photochemistry and Photobiology A: Chemistry 55, no. 2 (December 1990): 145–55. http://dx.doi.org/10.1016/1010-6030(90)80027-u.

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45

Rozanov, M., and M. Guelman. "Aeroassisted orbital maneuvering with variable structure control." Acta Astronautica 62, no. 1 (January 2008): 9–17. http://dx.doi.org/10.1016/j.actaastro.2006.12.025.

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46

Cramer, Janice A., Michael J. McGlinchey, and Jean-Yves Saillard. "Structural features of (C5H5)2Mo2S6 clusters: an EHMO study." Canadian Journal of Chemistry 67, no. 11 (November 1, 1989): 1931–35. http://dx.doi.org/10.1139/v89-300.

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Extended Hückel molecular orbital calculations on S6 in the planar D6h configuration and in the bent C2v geometry reveal that the former is favored for S62+ and the latter for S64−. It is shown that the additional six electrons would populate one π* and two σ* orbitals in the planar structure. In contrast, when these hexasulfur fragments are incorporated in triple-decker sandwich compounds the pseudo-D6h structure is favored for [(C5H5)Mo(S6)Mo(C5H5)]6+ but the C2v geometry is predicted for [(C5H5)Mo(S6)Mo(C5H5)]2+ which possesses only four more electrons. The required extra two electrons are shown to originate from a metallic δ-type molecular orbital. These EHMO calculations are in complete accord with some very recent experimental results from Gillespie's laboratory. Keywords: Molybdenum–sulfur clusters, EHMO calculations.

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47

Tanaka, Kiyoaki. "X-ray molecular orbital analysis. I. Quantum mechanical and crystallographic framework." Acta Crystallographica Section A Foundations and Advances 74, no. 4 (July 1, 2018): 345–56. http://dx.doi.org/10.1107/s2053273318005478.

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Molecular orbitals were obtained by X-ray molecular orbital analysis (XMO). The initial molecular orbitals (MOs) of the refinement were calculated by the ab initio self-consistent field (SCF) MO method. Well tempered basis functions were selected since they do not produce cusps at the atomic positions on the residual density maps. X-ray structure factors calculated from the MOs were fitted to observed structure factors by the least-squares method, keeping the orthonormal relationship between MOs. However, the MO coefficients correlate severely with each other, since basis functions are composed of similar Gaussian-type orbitals. Therefore, a method of selecting variables which do not correlate severely with each other in the least-squares refinement was devised. MOs were refined together with the other crystallographic parameters, although the refinement with the atomic positional parameters requires a lot of calculation time. The XMO method was applied to diformohydrazide, (NHCHO)2, without using polarization functions, and the electron-density distributions, including the maxima on the covalent bonds, were represented well. Therefore, from the viewpoint of X-ray diffraction, it is concluded that the MOs averaged by thermal vibrations of the atoms were obtained successfully by XMO analysis. The method of XMO analysis, combined with X-ray atomic orbital (AO) analysis, in principle enables one to obtain MOs or AOs without phase factors from X-ray diffraction experiments on most compounds from organic to rare earth compounds.

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48

Whangbo, Myung-Hwan, Hyun-Joo Koo, and Reinhard K. Kremer. "Spin Exchanges between Transition Metal Ions Governed by the Ligand p-Orbitals in Their Magnetic Orbitals." Molecules 26, no. 3 (January 20, 2021): 531. http://dx.doi.org/10.3390/molecules26030531.

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In this review on spin exchanges, written to provide guidelines useful for finding the spin lattice relevant for any given magnetic solid, we discuss how the values of spin exchanges in transition metal magnetic compounds are quantitatively determined from electronic structure calculations, which electronic factors control whether a spin exchange is antiferromagnetic or ferromagnetic, and how these factors are related to the geometrical parameters of the spin exchange path. In an extended solid containing transition metal magnetic ions, each metal ion M is surrounded with main-group ligands L to form an MLn polyhedron (typically, n = 3–6), and the unpaired spins of M are represented by the singly-occupied d-states (i.e., the magnetic orbitals) of MLn. Each magnetic orbital has the metal d-orbital combined out-of-phase with the ligand p-orbitals; therefore, the spin exchanges between adjacent metal ions M lead not only to the M–L–M-type exchanges, but also to the M–L…L–M-type exchanges in which the two metal ions do not share a common ligand. The latter can be further modified by d0 cations A such as V5+ and W6+ to bridge the L…L contact generating M–L…A…L–M-type exchanges. We describe several qualitative rules for predicting whether the M–L…L–M and M–L…A…L–M-type exchanges are antiferromagnetic or ferromagnetic by analyzing how the ligand p-orbitals in their magnetic orbitals (the ligand p-orbital tails, for short) are arranged in the exchange paths. Finally, we illustrate how these rules work by analyzing the crystal structures and magnetic properties of four cuprates of current interest: α-CuV2O6, LiCuVO4, (CuCl)LaNb2O7, and Cu3(CO3)2(OH)2.

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TERYAEV, O. V. "NUCLEON SPIN AND ORBITAL STRUCTURE: 20 YEARS LATER." Modern Physics Letters A 24, no. 35n37 (December 7, 2009): 2831–37. http://dx.doi.org/10.1142/s0217732309001042.

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The personal view on some recent aspects of average spin and orbital momenta of partons in nucleon is discussed and compared with the previous understanding. The special attention is payed to the strangeness polarization mediated by gluon anomaly and treatment of the strange quarks in a heavy ones in a multiscale nucleon. The crucial role in the orbital structure of nucleon is played by relocalization (Belinfante) invariance and Equivalence Principle (EP). The new manifestation of EP for spin 1 particles is suggested and discussed.

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Kasim, Thekra. "A Study of the electronic structure of CdS Nanocrystals using density functional theory." Iraqi Journal of Physics (IJP) 12, no. 24 (February 17, 2019): 25–32. http://dx.doi.org/10.30723/ijp.v12i24.317.

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Density Functional Theory at the generalized-gradient approximation level coupled with large unit cell method is used to simulate the electronic structure of (II-VI) zinc-blende cadmium sulfide nanocrystals that have dimensions 2-2.5 nm. The calculated properties include lattice constant, conduction and valence bands width, energy of the highest occupied orbital, energy of the lowest unoccupied orbital, energy gap, density of states etc. Results show that lattice constant and energy gap converge to definite values. However, highest occupied orbital, lowest unoccupied orbital fluctuates indefinitely depending on the shape of the nanocrystal.

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Journal articles on the topic 'Orbital structure'

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