Journal articles: 'Quantum theory of atoms in molecules'

1

Orville-Thomas, W. J. "Atoms in Molecules — a Quantum Theory." Journal of Molecular Structure: THEOCHEM 360, no. 1-3 (January 1996): 175. http://dx.doi.org/10.1016/s0166-1280(96)90925-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Potemkin, Vladimir, Nadezhda Palko, and Maria Grishina. "Quantum theory of atoms in molecules for photovoltaics." Solar Energy 190 (September 2019): 475–87. http://dx.doi.org/10.1016/j.solener.2019.08.048.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Wzgarda-Raj, Kinga, Agnieszka J. Rybarczyk-Pirek, Sławomir Wojtulewski, and Marcin Palusiak. "C—Br...S halogen bonds in novel thiourea N-oxide cocrystals: analysis of energetic and QTAIM parameters." Acta Crystallographica Section C Structural Chemistry 76, no. 2 (January 29, 2020): 170–76. http://dx.doi.org/10.1107/s2053229620000947.

Full text

Abstract:

Cocrystals of thiourea with 4-nitropyridine N-oxide, C5H4N2O3·2CH4N2S, (I), and 3-bromopyridine N-oxide, C5H4BrNO·CH4N2S, (II), crystallize in the monoclinic space group P21/c. In the crystals, molecules of both components are linked by N—H...O hydrogen bonds, creating R 2 1(6) synthons. The bromine substituent of the N-oxide component in (II) is a centre for C—Br...S halogen bonding to the thiourea molecule. Computations based on quantum chemistry methods (quantum theory of atoms in molecules, QTAIM) and atoms in molecules (AIM) theory were performed for a more detailed description of the observed type of halogen-bonding interaction.

APA, Harvard, Vancouver, ISO, and other styles

4

DELLE SITE, L. "ON THE RELEVANCE OF THE WAVEFUNCTION'S PHASE FACTOR FOR UNDERSTANDING TOPOLOGICAL PROPERTIES OF ATOMS AND MOLECULES IN CONDENSED PHASES: A SIMPLE EXAMPLE." International Journal of Modern Physics B 15, no. 04 (February 10, 2001): 403–8. http://dx.doi.org/10.1142/s0217979201004502.

Full text

Abstract:

In preceding work1,2 we proposed a criterion for defining atoms in molecules and in condensed phases based on the determination of the zero flux surface of the quantum current vector which holds the zero flux condition at every point. Here such a surface is calculated analytically in the simple case of a general hydrogen-like wavefunction with a non-constant phase factor. This simple example is then used as a basis to build an easy picture of the basic topological properties of atoms (or molecules) in multiatomic systems; these properties are particularly relevant for a molecular modeling procedure and a subsequent implementation in a simulation scheme. The main goal of this work is to underline with a simple example the importance of the wavefunction's phase factor in defining atoms or molecules in condensed systems (as it has been emphasized in our previous work); this point is important since a largely used theory (for defining atoms and molecules in condensed phases) such as the Bader's theory of atoms in molecules3 systematically neglects the properties of the wavefunction's phase factor.

APA, Harvard, Vancouver, ISO, and other styles

5

Krawczuk, Anna, Daniel Pérez, and Piero Macchi. "PolaBer: a program to calculate and visualize distributed atomic polarizabilities based on electron density partitioning." Journal of Applied Crystallography 47, no. 4 (June 14, 2014): 1452–58. http://dx.doi.org/10.1107/s1600576714010838.

Full text

Abstract:

This paper describes the program PolaBer, which calculates atomic polarizability tensors from electric field perturbations of a partitioned electron density distribution. Among many possible partitioning schemes, PolaBer is currently using the quantum theory of atoms in molecules and it is interfaced to programs that apply such a partitioning. The calculation of the atomic tensors follows the idea suggested by Keith [The Quantum Theory of Atoms in Molecules: From Solid State to DNA and Drug Design, (2007), edited by C. F. Matta & R. J. Boyd. Weinheim: Wiley-VCH], which enables the removal of the intrinsic origin dependence of the atomic charge contributions to the molecular dipole moment. This scheme allows the export, within chemically equivalent functional groups, of properties calculated from atomic dipoles, such as for example the atomic polarizabilities. The software permits visualization of the tensors and calculation of straightforward optical properties of a molecule (like the molar refractive index) or a crystal (assuming the molecule in a given crystal lattice).

APA, Harvard, Vancouver, ISO, and other styles

6

Foroutan-Nejad, Cina, Gholam Hossein Shafiee, Abdolreza Sadjadi, and Shant Shahbazian. "Ab initio charge density analysis of (B6C)2 and B4C3 species How to describe the bonding pattern?" Canadian Journal of Chemistry 84, no. 5 (May 1, 2006): 771–81. http://dx.doi.org/10.1139/v06-059.

Full text

Abstract:

In this study, a detailed topological charge density analysis based on the quantum theory of atoms in molecules (QTAIM) developed by Bader and co-workers, has been accomplished (using the B3LYP method) on the CB62 anion and three planar isomers of the C3B4 species, which had been first proposed by Exner and Schleyer as examples of molecules containing hexacoordinate carbon atoms. The analysis uncovers the strong (covalent) interactions of boron atoms as well as the "nondirectional" interaction of central carbon atom with those peripheral atoms. On the other hand, instabilities have been found in the topological networks of (B6C)2 and B4C3(para) species. A detailed investigation of these instabilities demonstrates that the topology of charge density has a floppy nature near the equilibrium geometries of the species under study. Thus, these species seems to be best described as complexes of a relatively concrete ring containing boron or carbon atoms and a central carbon atom that is confined in the plane of the molecule, but with nondirectional interactions with the surrounding atoms.Key words: hypervalency, hexacoordinate carbon, quantum theory of atoms in molecules, charge density analysis, ab initio methods.

APA, Harvard, Vancouver, ISO, and other styles

7

McWeeny, Roy. "The Quantum Mechanics of Cohesion." Collection of Czechoslovak Chemical Communications 72, no. 2 (2007): 252–68. http://dx.doi.org/10.1135/cccc20070252.

Full text

Abstract:

We consider the fundamental problem of "what makes atoms stick together in molecules, crystals, or clusters?" The Heitler and London paper (1927) on the hydrogen molecule marked a first attempt to discuss, in terms of quantum mechanics, the interaction of two atoms with unpaired spins. The aim of this note is to show how the primitive concepts used eighty years ago still retain a certain validity even in a much more general context. We consider in fact the interaction of two arbitrary systems, each with a resultant spin angular momentum, and show how the interaction energy depends on the scalar product of the two resultants. The actual nature of the two systems is irrelevant: they may be atoms, molecules, or ionic species of any kind each described by a wave function which may be, in principle, exact. This provides a first step in the formulation of any general theory of cohesion.

APA, Harvard, Vancouver, ISO, and other styles

8

TARASOV, VASILY E. "QUANTUM NANOTECHNOLOGY." International Journal of Nanoscience 08, no. 04n05 (August 2009): 337–44. http://dx.doi.org/10.1142/s0219581x09005517.

Full text

Abstract:

Nanotechnology is based on manipulations of individual atoms and molecules to build complex atomic structures. Quantum nanotechnology is a broad concept that deals with a manipulation of individual quantum states of atoms and molecules. Quantum nanotechnology differs from nanotechnology as a quantum computer differs from a classical molecular computer. The nanotechnology deals with a manipulation of quantum states in bulk rather than individually. In this paper, we define the main notions of quantum nanotechnology. Quantum analogs of assemblers, replicators and self-reproducing machines are discussed. We prove the possibility of realizing these analogs. A self-cloning (self-reproducing) quantum machine is a quantum machine which can make a copy of itself. The impossibility of ideally cloning an unknown quantum state is one of the basic rules of quantum theory. We prove that quantum machines cannot be self-cloning if they are Hamiltonian. There exist quantum non-Hamiltonian machines that are self-cloning machines. Quantum nanotechnology allows us to build quantum nanomachines. These nanomachines are not only small machines of nanosize. Quantum nanomachines should use new (quantum) principles of work.

APA, Harvard, Vancouver, ISO, and other styles

9

Grant, IP. "Current Developments in the Relativistic Quantum Mechanics of Atoms and Molecules." Australian Journal of Physics 39, no. 5 (1986): 649. http://dx.doi.org/10.1071/ph860649.

Full text

Abstract:

Current work in relativistic quantum mechanics by the author and his associates focusses on four topics: atomic structure theory using the GRASP package (Dyall 1986); extension of GRASP to handle electron continuum processes; the relation of quantum electrodynamics and relativistic quantum mechanics of atoms and molecules; and development of methods using finite basis set expansions for studying electronic structure of atoms and molecules. This paper covers only the last three topics, giving emphasis to growing points and outstanding difficulties.

APA, Harvard, Vancouver, ISO, and other styles

10

Kawamura, Kiyoshi, and Mikio Eto. "Theory of Artificial Atoms and Molecules using Semiconductor Quantum Dots." Japanese Journal of Applied Physics 38, Part 1, No. 1B (January 30, 1999): 366–71. http://dx.doi.org/10.1143/jjap.38.366.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Bader, R. F. W. "Topology and quantum theory of atoms in molecules and crystals." Acta Crystallographica Section A Foundations of Crystallography 52, a1 (August 8, 1996): C555. http://dx.doi.org/10.1107/s0108767396077380.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Smith, Ashlyn P., Adrienne E. McKercher, and Robert C. Mawhinney. "Inductive Effect: A Quantum Theory of Atoms in Molecules Perspective." Journal of Physical Chemistry A 115, no. 45 (November 17, 2011): 12544–54. http://dx.doi.org/10.1021/jp202757p.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Anderson, James S. M., Juan I. Rodríguez, Paul W. Ayers, and Andreas W. Götz. "Relativistic (SR-ZORA) quantum theory of atoms in molecules properties." Journal of Computational Chemistry 38, no. 2 (November 10, 2016): 81–86. http://dx.doi.org/10.1002/jcc.24520.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Guevara-Vela, José Manuel, Evelio Francisco, Tomás Rocha-Rinza , and Ángel Martín Pendás. "Interacting Quantum Atoms—A Review." Molecules 25, no. 17 (September 3, 2020): 4028. http://dx.doi.org/10.3390/molecules25174028.

Full text

Abstract:

The aim of this review is threefold. On the one hand, we intend it to serve as a gentle introduction to the Interacting Quantum Atoms (IQA) methodology for those unfamiliar with it. Second, we expect it to act as an up-to-date reference of recent developments related to IQA. Finally, we want it to highlight a non-exhaustive, yet representative set of showcase examples about how to use IQA to shed light in different chemical problems. To accomplish this, we start by providing a brief context to justify the development of IQA as a real space alternative to other existent energy partition schemes of the non-relativistic energy of molecules. We then introduce a self-contained algebraic derivation of the methodological IQA ecosystem as well as an overview of how these formulations vary with the level of theory employed to obtain the molecular wavefunction upon which the IQA procedure relies. Finally, we review the several applications of IQA as examined by different research groups worldwide to investigate a wide variety of chemical problems.

APA, Harvard, Vancouver, ISO, and other styles

15

Bartashevich, Ekaterina V., Ángel Martín Pendás, and Vladimir G. Tsirelson. "An anatomy of intramolecular atomic interactions in halogen-substituted trinitromethanes." Phys. Chem. Chem. Phys. 16, no. 31 (2014): 16780–89. http://dx.doi.org/10.1039/c4cp01257g.

Full text

Abstract:

The intramolecular interactions in substituted trinitromethanes, XC(NO₂)₃ (X = F, Cl, I, H) are studied and clarified by using a combination of the Quantum Theory of Atoms in Molecules (QTAIM), the non-covalent interaction analysis and the Interacting Quantum Atoms (IQA) methods.

APA, Harvard, Vancouver, ISO, and other styles

16

Blanco, M. A., A. Martín Pendás, and E. Francisco. "Interacting Quantum Atoms: A Correlated Energy Decomposition Scheme Based on the Quantum Theory of Atoms in Molecules." Journal of Chemical Theory and Computation 1, no. 6 (November 2005): 1096–109. http://dx.doi.org/10.1021/ct0501093.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Massa, Lou, Todd Keith, Youji Cheng, and Chérif F. Matta. "The kernel energy method applied to quantum theory of atoms in molecules – energies of interacting quantum atoms." Chemical Physics Letters 734 (November 2019): 136650. http://dx.doi.org/10.1016/j.cplett.2019.136650.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Hunter, Geoffrey. "Atoms in molecules from the exact one-electron wave function." Canadian Journal of Chemistry 74, no. 6 (June 1, 1996): 1008–13. http://dx.doi.org/10.1139/v96-113.

Full text

Abstract:

Use of the electron amplitude (i.e., the square root of the electron density) in place of the electron density in Bader's topological theory of atoms in molecules, is shown to lead to identical definitions of bond paths and interatomic surfaces. The concepts of regions of charge concentration and depletion, derived from the Laplacian of the electron density, become the concepts of classically allowed and forbidden regions of space when derived from the Laplacian of the electron amplitude, because the latter is the wave function in the exact Schrödinger equation for (any) one electron in the many-electron molecule. However, the domains of corresponding regions are different, the size and depth of a classically allowed region always being larger than the corresponding region of charge concentration; in some cases there is no region of charge concentration corresponding to a classically allowed region. The surface between the outermost allowed and forbidden regions of space provides a definition of the size and shape of the molecule. This definition of the outermost surface of the electronic charge cloud (the molecular envelope) is exact apart from quantum mechanical tunelling. Hence it is proposed as a basis for molecular graphics; i.e., as the unique, non-arbitrary, and, in principle, exact definition of the size and shape of a molecule. Key words: electron density, quantum chemistry, molecular graphics.

APA, Harvard, Vancouver, ISO, and other styles

19

Wilson, Timothy R., and M. E. Eberhart. "Quantum theory of atoms in molecules in condensed charge density space." Canadian Journal of Chemistry 97, no. 11 (November 2019): 757–62. http://dx.doi.org/10.1139/cjc-2019-0086.

Full text

Abstract:

By leveraging the fundamental doctrine of the quantum theory of atoms in molecules — the partitioning of the electron charge density (ρ) into regions bounded by surfaces of zero flux — we map the gradient field of ρ onto a two-dimensional space called the gradient bundle condensed charge density ([Formula: see text]). The topology of [Formula: see text] appears to correlate with regions of chemical significance in ρ. The bond wedge is defined as the image in ρ of the basin of attraction in [Formula: see text], analogous to the Bader atom, which is the basin of attraction in ρ. A bond bundle is defined as the union of bond wedges that share interatomic surfaces. We show that maxima in [Formula: see text] typically map to bond paths in ρ, though this is not necessarily always true. This observation addresses many of the concerns regarding the chemical significance of bond critical points and bond paths in the quantum theory of atoms in molecules.

APA, Harvard, Vancouver, ISO, and other styles

20

Ehouman, Ahissandonatien, Adjoumanirodrigue Kouakou, Fatogoma Diarrassouba, Hakim Abdel Aziz Ouattara, and Paulin Marius Niamien. "Study of the Stability and Chemical Reactivity of a Series of Tetrazole Pyrimidine Hybrids by the Density Functional Theory Method (DFT)." Oriental Journal Of Chemistry 37, no. 4 (August 30, 2021): 805–12. http://dx.doi.org/10.13005/ojc/370406.

Full text

Abstract:

Our theoretical study of stability and reactivity was carried out on six (06) molecules of a series of pyrimidine tetrazole hybrids (PTH) substituted with H, F, Cl, Br, OCH3 and CH3 atoms and groups of atoms using the density function theory (DFT). Analysis of the thermodynamic formation quantities confirmed the formation and existence of the series of molecules studied. Quantum chemical calculations at the B3LYP / 6-311G (d, p) level of theory determined molecular descriptors. Global reactivity descriptors were also determined and analyzed. Thus, the results showed that the compound PTH_1 is the most stable, and PTH_5 is the most reactive and nucleophilic. Similarly, the compound PTH_4 is the most electrophilic. The analysis of the local descriptors and the boundary molecular orbitals allowed us to identify the preferred atoms for electrophilic and nucleophilic attacks.

APA, Harvard, Vancouver, ISO, and other styles

21

Lu, K. U. "Superconductivity Deduced from Deterministic Theory of Atomic Structure." International Journal of Modern Physics B 12, no. 29n31 (December 20, 1998): 3113–18. http://dx.doi.org/10.1142/s0217979298002179.

Full text

Abstract:

The standard Quantum Mechanics is statistical in nature and cannot provide a detailed picture of an atom. The Deterministic Theory of Atomic Structure, derived from a system of equations that govern the electrodynamics in atoms, can account for the stability of the atoms. We describe the chirality of an atom, the rules for forming molecules, and the assemblies of the superconducting material from Aluminum and Silicon.

APA, Harvard, Vancouver, ISO, and other styles

22

Vallejos, Margarita M., and Silvina C. Pellegrinet. "Competing mechanisms for the reaction of dichloropropynylborane with 2-tert-butylbutadiene. Diels–Alder reaction versus alkynylboration." RSC Advances 5, no. 86 (2015): 70147–55. http://dx.doi.org/10.1039/c5ra12903f.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Tsirelson, Vladimir G., Anastasia V. Shishkina, Adam I. Stash, and Simon Parsons. "The experimental and theoretical QTAIMC study of the atomic and molecular interactions in dinitrogen tetroxide." Acta Crystallographica Section B Structural Science 65, no. 5 (August 28, 2009): 647–58. http://dx.doi.org/10.1107/s0108768109028821.

Full text

Abstract:

The atomic and molecular interactions in a crystal of dinitrogen tetraoxide, α-N2O4, have been studied in terms of the quantum topological theory of molecular structure using high-resolution, low-temperature X-ray diffraction data. The experimental electron density and electrostatic potential have been reconstructed with the Hansen–Coppens multipole model. In addition, the three-dimensional periodic electron density of crystalline α-N2O4 has been calculated at the B3LYP/cc-pVDZ level of theory with and without the geometry optimization. The application of the quantum theory of atoms in molecules and crystals (QTAIMC) recovered the two types of intermolecular bond paths between O atoms in crystalline α-N2O4, one measuring 3.094, the other 3.116 Å. The three-dimensional distribution of the Laplacian of the electron density around the O atoms showed that the lumps in the negative Laplacian fit the holes on the O atoms in the adjacent molecules, both atoms being linked by the intermolecular bond paths. This shows that the Lewis-type molecular complementarity contributes significantly to intermolecular bonding in crystalline N2O4. Partial overlap of atomic-like basins created by zero-flux surfaces in both the electron density and the electrostatic potential show that attractive electrostatic interaction exists between O atoms even though they carry the same net formal charge. The exchange and correlation contributions to the potential energy density were also computed by means of the model functionals, which use the experimental electron density and its derivatives. It was found that the intermolecular interactions in α-N2O4 are accompanied by the correlation energy-density `bridges' lowering the local potential energy along the intermolecular O...O bond paths in the electron density, while the exchange energy density governs the shape of bounded molecules.

APA, Harvard, Vancouver, ISO, and other styles

24

Takatsuka, Kazuo. "Quantum Chaos in the Dynamics of Molecules." Entropy 25, no. 1 (December 29, 2022): 63. http://dx.doi.org/10.3390/e25010063.

Full text

Abstract:

Quantum chaos is reviewed from the viewpoint of “what is molecule?”, particularly placing emphasis on their dynamics. Molecules are composed of heavy nuclei and light electrons, and thereby the very basic molecular theory due to Born and Oppenheimer gives a view that quantum electronic states provide potential functions working on nuclei, which in turn are often treated classically or semiclassically. Therefore, the classic study of chaos in molecular science began with those nuclear dynamics particularly about the vibrational energy randomization within a molecule. Statistical laws in probabilities and rates of chemical reactions even for small molecules of several atoms are among the chemical phenomena requiring the notion of chaos. Particularly the dynamics behind unimolecular decomposition are referred to as Intra-molecular Vibrational energy Redistribution (IVR). Semiclassical mechanics is also one of the main research fields of quantum chaos. We herein demonstrate chaos that appears only in semiclassical and full quantum dynamics. A fundamental phenomenon possibly giving birth to quantum chaos is “bifurcation and merging” of quantum wavepackets, rather than “stretching and folding” of the baker’s transformation and the horseshoe map as a geometrical foundation of classical chaos. Such wavepacket bifurcation and merging are indeed experimentally measurable as we showed before in the series of studies on real-time probing of nonadiabatic chemical reactions. After tracking these aspects of molecular chaos, we will explore quantum chaos found in nonadiabatic electron wavepacket dynamics, which emerges in the realm far beyond the Born-Oppenheimer paradigm. In this class of chaos, we propose a notion of Intra-molecular Nonadiabatic Electronic Energy Redistribution (INEER), which is a consequence of the chaotic fluxes of electrons and energy within a molecule.

APA, Harvard, Vancouver, ISO, and other styles

25

Grebenyuk, A. G. "Island-type structures with hypercoordinated atoms." SURFACE 14(29) (December 30, 2022): 3–36. http://dx.doi.org/10.15407/surface.2022.14.003.

Full text

Abstract:

Experimental data and the results of theoretical modeling of the spatial structure and chemical properties of isolated particles (molecules and clusters) characterized by the presence of hypercoordinated atoms and the molecular crystals formed by them have been analyzed. Methods of describing the distribution of electron density in molecular crystals and their polymorphism are considered. The influence of the chemical nature of the molecules of binary compounds on their capability to associate and form clusters is described, and the transition from dispersion interaction to coordination bonds in such structures is traced.The review highlights the properties of many dimers, trimers and oligomers of hydrides and halides of chemical elements of different valence, clusters of elemental-organic and coordination (both inorganic and organic nature) compounds, polyhedral structures with non-classical coordination of atoms, in particular, metal carbohedrenes. The results of quantum chemical calculations using the methods of Hartree-Fock (HF), configurational interaction, electron density functional theory (DFT) and second-order Möller-Plesset perturbation theory (MP2) of the spatial structure and energy characteristics of the considered models are discussed. Theoretical results are compared with available experimental data.

APA, Harvard, Vancouver, ISO, and other styles

26

Wilson, Timothy R., Anastassia N. Alexandrova, and M. E. Eberhart. "Electron Density Geometry and the Quantum Theory of Atoms in Molecules." Journal of Physical Chemistry A 125, no. 50 (December 15, 2021): 10622–31. http://dx.doi.org/10.1021/acs.jpca.1c09359.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Pendás, A. Martı́n, M. A. Blanco, and E. Francisco. "Two-electron integrations in the quantum theory of atoms in molecules." Journal of Chemical Physics 120, no. 10 (March 8, 2004): 4581–92. http://dx.doi.org/10.1063/1.1645788.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Matta, Chérif F., Martin Sichinga, and Paul W. Ayers. "Information theoretic properties from the quantum theory of atoms in molecules." Chemical Physics Letters 514, no. 4-6 (October 2011): 379–83. http://dx.doi.org/10.1016/j.cplett.2011.08.072.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

da Silva, Natieli Alves, Luiz Alberto Terrabuio, and Roberto Luiz Andrade Haiduke. "A quantum theory atoms in molecules investigation of Lewis base protonation." International Journal of Quantum Chemistry 117, no. 3 (October 21, 2016): 197–207. http://dx.doi.org/10.1002/qua.25310.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Mølmer, Klaus. "The quantum vibes of atoms and ichthyosaurs." Muzikologija, no. 24 (2018): 51–59. http://dx.doi.org/10.2298/muz1824051m.

Full text

Abstract:

The quantum mechanical description of microscopic phenomena treats minuscule particles as waves and explains why atoms and molecules absorb and emit radiation at particular frequencies. This article reviews the physical theory of waves and discusses similarities between atoms and musical instruments. In particular, it describes how we may identify new musical scales and harmonies and play atomic music by translating and scaling the frequencies in the atomic world to the audible spectrum.

APA, Harvard, Vancouver, ISO, and other styles

31

Azizi, Alireza, Roya Momen, Tianlv Xu, Steven R. Kirk, and Samantha Jenkins. "Non-nuclear attractors in small charged lithium clusters, Limq (m = 2–5, q = ±1), with QTAIM and the Ehrenfest force partitioning." Physical Chemistry Chemical Physics 20, no. 38 (2018): 24695–707. http://dx.doi.org/10.1039/c8cp05214j.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Bader, R. F. W. "Properties of atoms and bonds in carbocations." Canadian Journal of Chemistry 64, no. 6 (June 1, 1986): 1036–45. http://dx.doi.org/10.1139/v86-174.

Full text

Abstract:

The quantum theory of atoms in molecules defines structures for and determines the properties of the atoms and bonds in the series of carbocations [(CH3)nCH3−n]+ with n = 0–3, and their parent hydrocarbons. In this theory, an atom in a molecule and its properties are defined by quantum mechanics. The quantum condition defining the atom is given in terms of a property derived from the charge density, as are the other concepts of the molecular structure hypothesis. In terms of the amount of electronic charge density accumulated between the carbon nuclei and its spatial distribution, a C—C bond of the carbocations exhibits an order greater than one. There is a transfer of charge from the hydrogens of methyl to the central carbon that destroys the axial symmetry of these C—C bonds and concentrates the charge in a plane perpendicular to the plane of substitution, in a manner consistent with the hyperconjugative mechanism of electron transfer. The positive charge of a carbocation is thus delocalized over all the atoms in the molecule, and the extent of this delocalization increases with increased methyl substitution. The electron population of each atom in a carbocation increases with this increase in the delocalization of positive charge and its energy is correspondingly decreased (the atom becomes more stable). These effects are most pronounced for the carbon atom bearing the methyl groups and they account for the observed increase in the relative stabilities of the carbocations with increasing methyl substitution. The electron populations and energies of the atoms in saturated hydrocarbons are also determined. The group additivity scheme for the energy in the homologous series of normal alkanes is predicted and explained in terms of the properties of the quantum atoms. It is the possibility of such transferability of the quantum atoms and their properties between systems that identifies them with the atoms of chemistry.

APA, Harvard, Vancouver, ISO, and other styles

33

Costa, Fabio Luiz Paranhos, Sidnei Bessa de Oliveira Fernandes, Catharina Eccard Fingolo, Fabio Boylan, Antônio M. de J. Chaves Neto, Gunar Vingre da Silva Mota, Breno Almeida Soares, Marcelo Ricardo Souza Siqueira, and Thaís Forest Giacomello. "Experimental and Theoretical Nuclear Magnetic Resonance Data from Tryptanthrin, an Alkaloid with Potential Activity Against Human Coronavirus." Advanced Science, Engineering and Medicine 12, no. 7 (July 1, 2020): 963–69. http://dx.doi.org/10.1166/asem.2020.2638.

Full text

Abstract:

Coronaviruses belong to the subfamily Coronavirinae, which are large viruses with a single Ribonucleic acid tape and a nucleocapsid. In a recent study it was found that the molecule of tryptanthrin has antiviral potential against human coronavirus NL63. In this work, we used a combination of theoretical techniques with experimental nuclear magnetic resonance data to assist in the structural characterization of the Tryptanthrin molecule. Tryptanthrin was extracted from Couroupita guianensis leaves. The theoretical calculations of hydrogen-1, homonuclear spin–spin coupling constants and the quantum theory of atoms in molecules were performed employing density functional theory. Our results show that the hydrogen-1 chemical shifts calculated at the gaseous phase and solvent presented similar performance. The quantum theory of atoms in molecules calculations was able to quantify and qualify bonded interactions based on five topological parameters obtained at the analyzed bond critical point to tryptanthrin molecule. We obtained a satisfactory correlation between tryptanthrin delocalization index values and its experimental and calculated proton–proton coupling constants. In conclusion, the theoretical techniques used in this work in combination with NMR experimental data can be a useful tool in aiding the structural determination of organic compounds.

APA, Harvard, Vancouver, ISO, and other styles

34

Breid, B. M., and J. R. Anglin. "Quantum fluctuations in the time-dependent BCS–BEC crossover." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1877 (June 5, 2008): 2813–20. http://dx.doi.org/10.1098/rsta.2008.0082.

Full text

Abstract:

We describe the time-dependent formation of a molecular Bose–Einstein condensate from a BCS state of fermionic atoms as a result of slow sweeping through a Feshbach resonance. We apply a path integral approach for the molecules, and use two-body adiabatic approximations to solve the atomic evolution in the presence of the classical molecular fields, obtaining an effective action for the molecules. In the narrow resonance limit, the problem becomes semiclassical, and we discuss the growth of the molecular condensate in the saddle point approximation. Considering this time-dependent process as an analogue of the cosmological Zurek scenario, we compare the way condensate growth is driven in this rigorous theory with its phenomenological description via time-dependent Ginzburg–Landau theory.

APA, Harvard, Vancouver, ISO, and other styles

35

Tamulis, Arvydas, Vykintas Tamulis, and Aiste Ziriakoviene. "Quantum Mechanical Design of Molecular Computers Elements Suitable for Self-Assembling to Quantum Computing Living Systems." Solid State Phenomena 97-98 (April 2004): 173–80. http://dx.doi.org/10.4028/www.scientific.net/ssp.97-98.173.

Full text

Abstract:

There are presented logic gates of molecular electronics digital computers. Maximal length of these molecular electronics digital logic gates are no more than four nanometers and maximal width 2.5 nm. The results of light induced internal molecular motions in azo-dyes molecules have been used for the design of light driven logically controlled (OR, AND) molecular machines composed from organic photoactive electron donor dithieno[3,2-b:2',3'-d]thiophene and ferrocene molecules, electron accepting tetracyano-indane molecule, and moving azo-benzene molecular fragment. Density functional theory (DFT) B3PW91/6-311G model calculations were performed for the geometry optimization of these molecular electronics logical gates. Applied DFT time dependent (DFT-TD/B3PW91) method and our visualization program give absorption spectra of designed molecular gates and show from which fragments electrons are hopping in various excited states. Quantum mechanical investigations of proton Nuclear Magnetic Resonance (NMR) values of Cu, Co, Zn, Mn and Fe biliverdin derivatives and their dimers using ab initio Hartree-Fock (HF) and DFT methods indicate that these modified derivatives should generate from one to twelve Quantum Bits (QuBits). The chemical shifts are obtained as the difference of the values of the tetramethylsilane (Si(CH3)4) molecule Gauge-Independent Atomic Orbital (GIAO) nuclear magnetic shielding tensor on the hydrogen atoms and that of the magnetically active molecules. There are designed several single supermolecule and supramolecular devices containing molecular electronics digital logic gates, photoactive molecular machines and elements of molecular NMR quantum computers that allowed to design several supramolecular Control NOT NMR quantum computing gates. Self-assembling simulations of these molecular quantum computing gates induced idea of self-assembled molecular quantum supercomputer and molecular quantum computing life.

APA, Harvard, Vancouver, ISO, and other styles

36

Saraf, Sarvin Hossien, and Reza Ghiasi. "Quantum theory of atoms in molecules, electron localization function, and localized-orbital locator investigations on trans-(NHC)PtI2(para-NC5H4X) complexes." Journal of Chemical Research 44, no. 7-8 (February 17, 2020): 482–86. http://dx.doi.org/10.1177/1747519820907243.

Full text

Abstract:

In this study, the MPW1PW91 method is applied to analyze the quantum theory of atoms in molecules, the electron localization function, and the localized-orbital locator in trans-(NHC)PtI2( para-NC5H4X) (X = H, F, COOH, CN, NO2, Me, OH, NH2) complexes. The substituent effect is assessed in the presence of electron-withdrawing groups and electron-donating groups and their influence on the Pt–C and Pt–N bonds of the molecules is analyzed using quantum theory of atoms in molecules, electron localization function, and localized-orbital locator methods. In addition, the eta index (η) is used to evaluate the Pt–C and Pt–N bonds in the studied complexes. The correlations between electron localization function, localized-orbital locator, and the η index values of Pt–C and Pt–N bonds with Hammett constants (σp) and dual parameters (σI and σR) are given.

APA, Harvard, Vancouver, ISO, and other styles

37

Macchi, Piero. "The future of topological analysis in experimental charge-density research." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 73, no. 3 (June 1, 2017): 330–36. http://dx.doi.org/10.1107/s2052520617006989.

Full text

Abstract:

In a recent paper, Dittrich (2017) critically discussed the benefits of analysing experimental electron density within the framework of the quantum theory of atoms in molecules, often called simply the topological analysis of the charge density. The point he raised is important because it challenges the scientific production of a very active community. The question whether this kind of investigation is still sensible is intriguing and it fosters a multifaceted answer. Granted that none can predict the future of any field of science, but an alternative point of view emerges after answering three questions: Why should we investigate the electron charge (and spin) density? Is the interpretative scheme proposed by the quantum theory of atoms in molecules useful? Is an experimental charge density necessary?

APA, Harvard, Vancouver, ISO, and other styles

38

Martín Pendás, A., M. A. Blanco, and E. Francisco. "Revisiting the variational nature of the quantum theory of atoms in molecules." Chemical Physics Letters 417, no. 1-3 (January 2006): 16–21. http://dx.doi.org/10.1016/j.cplett.2005.09.113.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Anderson, James S. M., and Paul W. Ayers. "Quantum Theory of Atoms in Molecules: Results for the SR-ZORA Hamiltonian." Journal of Physical Chemistry A 115, no. 45 (November 17, 2011): 13001–6. http://dx.doi.org/10.1021/jp204558n.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Heidar Zadeh, Farnaz, and Shant Shahbazian. "The quantum theory of atoms in positronic molecules: The subsystem variational procedure." International Journal of Quantum Chemistry 111, no. 9 (October 6, 2010): 1999–2013. http://dx.doi.org/10.1002/qua.22881.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Ley Koo, Eugenio. "Recent Progress in Confined Atoms and Molecules: Superintegrability and Symmetry Breakings." Revista Mexicana de Física 64, no. 4 (June 28, 2018): 326. http://dx.doi.org/10.31349/revmexfis.64.326.

Full text

Abstract:

This review article has the antecedents of Jaskolski’s 1996 Physics Report Confined Many-electron Systems , the fifteen chapters on the Theory of Confined Quantum Systems in Vols. 57 and 58 of 2009 Advances in Quantum Chemistry, and the nine chapters of the 2014 Monograph “Electronic Structure of Confined Quantum Atoms and Molecules”. In this contribution the last two sets of reviews are taken as the points of reference to illustrate some advances in several lines of research in the elapsed periods. The recent progress is illustrated on the basis of a selection of references from the literature taking into account the confined quantum systems, the confining environments and their modelings; their properties and processes, emphasizing the changes due to the confinement; the methods of analysis and solutions, their results including confiability and accuracy; as well as applications in other areas. The updated and current works of the Reviewer are also presented. The complementary words in the title apply to the simplest atom in its free configuration and to the harmonic oscillator quantum dot because they admit more exact solutions than the number of their degrees of freedom; and to their many-electron and confined counterparts, due to their additional interactions and changes in boundary conditions.

APA, Harvard, Vancouver, ISO, and other styles

42

Loncke, Paul G., Timothy A. Gadosy, and Gilles H. Peslherbe. "A theoretical study of the mechanism of 1,2-migrations in methoxysiloxycarbene." Canadian Journal of Chemistry 80, no. 3 (March 1, 2002): 302–14. http://dx.doi.org/10.1139/v02-013.

Full text

Abstract:

Intramolecular rearrangements of methoxysiloxycarbene (CH3OCOSiH3) have been investigated by means of ab initio molecular orbital theory and hybrid density functional theory calculations. Particular attention was paid to 1,2-silyl migration from oxygen to the carbene carbon, and to the analogous 1,2-methyl migration for comparison. A combination of frontier molecular orbital (FMO) theory, natural bond orbital (NBO) analysis, and the theory of atoms in molecules (AIM) were used to shed light on the mechanistic details of these rearrangements. The present analyses clearly indicate that 1,2-silyl migration involves nucleophilic attack by the carbene lone pair at silicon, whereas 1,2-methyl migration seems to involve an anion-like shift of the methyl group from oxygen to the "vacant" carbene p-orbital. Finally, based on the computed relative Gibbs free energy barriers, it is apparent that 1,2-silyl migration is much more favorable than 1,2-methyl migration, in keeping with experimental observations.Key words: carbenes, oxycarbenes, intramolecular rearrangements, 1,2-migrations, quantum chemistry, theory of atoms in molecules, natural bond orbital analysis

APA, Harvard, Vancouver, ISO, and other styles

43

Abbaz, Tahar, Amel Bendjeddou, and Didier Villemin. "Structural and quantum chemical studies on aryl sulfonyl piperazine derivatives." Journal of Drug Delivery and Therapeutics 9, no. 1-s (February 15, 2019): 88–97. http://dx.doi.org/10.22270/jddt.v9i1-s.2264.

Full text

Abstract:

The optimized molecular structure and electronic features of aryl sulfonyl piperazine derivatives 1-4 have been investigated theoretically using Gaussian 09 software package and DFT/B3LYP method with 6-31G (d,p) basis set. The reactivity of the title molecules was investigated and both the positive and negative centers of the molecules were identiﬁed using molecular electrostatic potential (MEP) analysis which the results illustrate that the regions reveal the negative electrostatic potential are localized in sulfamide function while the regions presenting the positive potential are localized in the hydrogen atoms. The energies of the frontier molecular orbitals and LUMO-HOMO energy gap are measured to explain the electronic transitions. Global reactivity parameters of the aryl sulfonyl piperazine derivatives molecules were predicted to find that the more reactive and softest compound is the compound 3. Mulliken’s net charges have been calculated and results show that 3N is the more negative and 33S is the more positive charge, which Indicates extensive charge delocalization in the entire molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization (π→π transitions) has been analyzed using NBO analysis. Fist hyperpolarizability is calculated in order to ﬁnd its importance in non-linear optics and the results show that the studied molecules have not the NLO applications. Keywords: sulfamide; density functional theory; computational chemistry; electronic structure; quantum chemical calculations.

APA, Harvard, Vancouver, ISO, and other styles

44

Fitzsimmons, Amelia, and Mariusz Klobukowski. "Basis set effects in simple compounds of heavy rare gases." Canadian Journal of Chemistry 91, no. 9 (September 2013): 894–901. http://dx.doi.org/10.1139/cjc-2012-0510.

Full text

Abstract:

Rare-gas hydrides of the type HRgX (Rg = Xe or Rn and X = F, Cl, Br, or I) have been studied using Møller–Plesset and density functional theory methods. Six model core potentials and their associated basis sets were used, with relativistic effects included implicitly. The effects of polarization, correlating, and diffuse basis functions were investigated. Molecular geometries of the metastable hydrides and transition states along the decomposition pathway were computed together with corresponding energies of formation and decomposition. The results of quantum theory of atoms in molecules analysis further elucidate the interactions between atoms in HRgX species and confirm the results of analyses obtained from the natural bond orbitals approach.

APA, Harvard, Vancouver, ISO, and other styles

45

Munshi, Parthapratim, and Tayur N. Guru Row. "Intra- and intermolecular interactions in small bioactive molecules: cooperative features from experimental and theoretical charge-density analysis." Acta Crystallographica Section B Structural Science 62, no. 4 (July 12, 2006): 612–26. http://dx.doi.org/10.1107/s0108768106017393.

Full text

Abstract:

The topological features of the charge densities, ρ(r), of three bioactive molecules, 2-thiouracil [2,3-dihydro-2-thioxopyrimidin-4(1H)-one], cytosine [4-aminopyrimidin-2(1H)-one] monohydrate and salicylic acid (2-hydroxybenzoic acid), have been determined from high-resolution X-ray diffraction data at 90 K. The corresponding results are compared with the periodic theoretical calculations, based on theoretical structure factors, performed using DFT (density-functional theory) at the B3LYP/6-31G** level. The molecules pack in the crystal lattices via weak intermolecular interactions as well as strong hydrogen bonds. All the chemical bonds, including the intra- and intermolecular interactions in all three compounds, have been quantitatively described by topological analysis based on Bader's quantum theory of `Atoms In Molecules'. The roles of interactions such as C—H...O, C—H...S, C—H...π and π...π have been investigated quantitatively in the presence of strong hydrogen bonds such as O—H...O, N—H...O and N—H...S, based on the criteria proposed by Koch and Popelier to characterize hydrogen bonds and van der Waals interactions. The features of weak intermolecular interactions, such as S...S in 2-thiouracil, the hydrogen bonds generated from the water molecule in cytosine monohydrate and the formation of the dimer via strong hydrogen bonds in salicylic acid, are highlighted on a quantum basis. Three-dimensional electrostatic potentials over the molecular surfaces emphasize the preferable binding sites in the structure and the interaction features of the atoms in the molecules, which are crucial for drug–receptor recognition.

APA, Harvard, Vancouver, ISO, and other styles

46

Mertsalov, Dmitriy F., Rosa M. Gomila, Vladimir P. Zaytsev, Mikhail S. Grigoriev, Eugeniya V. Nikitina, Fedor I. Zubkov, and Antonio Frontera. "On the Importance of Halogen Bonding Interactions in Two X-ray Structures Containing All Four (F, Cl, Br, I) Halogen Atoms." Crystals 11, no. 11 (November 18, 2021): 1406. http://dx.doi.org/10.3390/cryst11111406.

Full text

Abstract:

This manuscript reports the synthesis and X-ray characterization of two octahydro-1H-4,6-epoxycyclopenta[c]pyridin-1-one derivatives that contain the four most abundant halogen atoms (Ha) in the structure with the aim of studying the formation of Ha···Ha halogen bonding interactions. The anisotropy of electron density at the heavier halogen atoms provokes the formation of multiple Ha···Ha contacts in the solid state. That is, the heavier Ha-atoms exhibit a region of positive electrostatic potential (σ-hole) along the C–Ha bond and a belt of negative electrostatic potential (σ-lumps) around the atoms. The halogen bonding assemblies in both compounds were analyzed using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, the quantum theory of “atom-in-molecules” (QTAIM), the noncovalent interaction plot (NCIplot), and the electron localization function (ELF).

APA, Harvard, Vancouver, ISO, and other styles

47

García-Revilla, Marco, E. Francisco, A. Costales, and A. Martín Pendás. "Performance of the Density Matrix Functional Theory in the Quantum Theory of Atoms in Molecules." Journal of Physical Chemistry A 116, no. 4 (September 27, 2011): 1237–50. http://dx.doi.org/10.1021/jp204001n.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Moreno, Norberto, Cacier Z. Hadad, and Albeiro Restrepo. "Microsolvation of electrons by a handful of ammonia molecules." Journal of Chemical Physics 157, no. 13 (October 7, 2022): 134301. http://dx.doi.org/10.1063/5.0107245.

Full text

Abstract:

Microsolvation of electrons in ammonia is studied here via anionic [Formula: see text] clusters with n = 2–6. Intensive samplings of the corresponding configurational spaces using second-order perturbation theory with extended basis sets uncover rich and complex energy landscapes, heavily populated by many local minima in tight energy windows as calculated from highly correlated coupled cluster methods. There is a marked energetical preference for structures that place the excess electron external to the molecular frame, effectively coordinating it with the three protons from a single ammonia molecule. Overall, as the clusters grow in size, the lowest energy dimer serves as the basic motif over which additional ammonia molecules are attached via unusually strong charge-assisted hydrogen bonds. This is a priori quite unexpected because, on electrostatic grounds, the excess electron would be expected to be in contact with as many protons as possible. Accordingly, a full quantum mechanical treatment of the bonding interactions under the tools provided by the quantum theory of atoms in molecules is carried out in order to dissect and understand the nature of intermolecular contacts. Vertical detachment energies reveal bound electrons even for n = 2.

APA, Harvard, Vancouver, ISO, and other styles

49

Reibnegger, Gilbert. "An ab initio and density functional theory study on neutral pterin radicals." Pteridines 26, no. 4 (December 1, 2015): 135–42. http://dx.doi.org/10.1515/pterid-2015-0008.

Full text

Abstract:

AbstractThe electronic structures of the five radicals resulting from homolytic elimination of one of the hydrogen atoms from the most stable tautomeric form of neutral pterin were investigated in gas phase as well as in aqueous solution. Molecular wave functions obtained by density functional theory were analysed by quantum theory of atoms in molecules and electron localisation functions (ELF). Spin densities of the radicals as well as electrostatic potential functions were analysed. Radicals resulting from elimination of N-bonded hydrogen atoms are more stable in comparison with radicals obtained after abstraction of C-bonded hydrogen atoms. N-centred radicals show strong delocalisation of spin density over both heteroaromatic rings; in C-centred radicals delocalisation does not occur. ELF analyses showed that in N-derived radicals particularly the lone electron pair at N2′ is strongly involved into the bicyclic heteroaromatic π-electron system. Thereby, bonding geometry at N2′ in these radicals changes from pyramidal to planar. Transition from gas phase to solution phase (water) generally leads to increased polarity of the structures. Pterin-derived free radicals have been implicated in several biologically important reactions; so this investigation provides first insights into the detailed electronic structures of such molecular systems.

APA, Harvard, Vancouver, ISO, and other styles

50

Yang, H. H., F. C. Jin, and L. M. Wei. "The hydrogen bonding characteristic of (H2O)n (n=14-17)：quantum theory of atoms in molecules." Digest Journal of Nanomaterials and Biostructures 16, no. 4 (December 2021): 1401–9. http://dx.doi.org/10.15251/djnb.2021.164.1401.

Full text

Abstract:

The hydrogen bonding characteristics of water clusters (H2O)n (n=14-17) are investigated by using Quantum Theory of Atoms in Molecules (QTAIM). The stabilities of the water clusters are related to the strength and number of hydrogen bonding. The strength of hydrogen bonding is primarily concerned with the characteristic of the donor molecule. The electron densities of bonding critical points of hydrogen bonding formed by DAA, DDAA and DDA molecule as hydrogen-donor (H-donor) are about 0.045 a.u., 0.035 a.u. and 0.025 a.u. respectively. The strength of hydrogen bonding formed by DAA as H-donor is the strongest, and that formed by DDA as H-donor is the weakest. The strength of hydrogen bonding in pentagonal rings is stronger than that in the cubes.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Quantum theory of atoms in molecules'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles