Improved lower bounds for the atomic charge density at the nucleus

A direct relation between the charge density of a free atom, ρa(r), and the cohesive energy of the corresponding metal is proposed. This relation is based on an approximation for the metallic charge density, ρm(r), that is constructed from ρa(r) through [Formula: see text] being the atomic volume of the metallic atom, and R0 the corresponding Wigner–Seitz radius. The cohesive energy Ecoh is then related to [Formula: see text] through [Formula: see text] A systematic study of 29 metallic elements including the 3d and 4d transition elements shows that the proposed relation is, in general, at least as accurate as recent ab initio results. In the same fashion, an expression for the metallic bulk modulus is derived. This expression requires, in addition to [Formula: see text], the values of ρa(R0) and its first derivative ρ′a(R0). The computed bulk moduli are, again, at least as good as the ab initio ones for the set of metallic elements studied. Key words: cohesive energies, bulk moduli, charge density, transition elements.

Download Full-text

A Bond Bundle Case Study of Diels-Alder Catalysis Using Oriented Electric Fields

10.26434/chemrxiv-2021-17wpx-v2 ◽

2022 ◽

Author(s):

Timothy Wilson ◽

Mark Eberhart

Keyword(s):

Electric Field ◽

Charge Density ◽

Electric Fields ◽

Chemical Reactions ◽

Catalytic Effect ◽

Reaction Pathway ◽

Three Dimensional ◽

Atomic Charge ◽

Diels Alder

Bond bundles are chemical bonding regions, analogous to Bader atoms, uniquely defined according to the topology of the gradient bundle condensed charge density, itself obtained by a process of infinitesimal partitioning of the three-dimensional charge density into differential zero-flux surface bounded regions. Here we use bond bundle analysis to investigate the response of the charge density to an oriented electric field in general, and the catalytic effect of such a field on Diels-Alder reactions in particular, which in this case is found to catalyze by allowing the transition state valance bond bundle configuration to be achieved earlier along the reaction pathway. Using precise numerical values, we arrive at the conclusion that chemical reactions and electric field catalysis can be understood in terms of intra-atomic charge density redistribution, i.e., that charge shifts within more so than between atoms account for the making and breaking of bonds.

Download Full-text

A Bond Bundle Case Study of Diels-Alder Catalysis Using Oriented Electric Fields

10.26434/chemrxiv-2021-17wpx ◽

2021 ◽

Author(s):

Timothy Wilson ◽

Mark Eberhart

Keyword(s):

Electric Field ◽

Charge Density ◽

Electric Fields ◽

Chemical Reactions ◽

Catalytic Effect ◽

Reaction Pathway ◽

Three Dimensional ◽

Atomic Charge ◽

Diels Alder

Bond bundles are chemical bonding regions, analogous to Bader atoms, uniquely defined according to the topology of the gradient bundle condensed charge density, itself obtained by a process of infinitesimal partitioning of the three-dimensional charge density into differential zero-flux surface bounded regions. Here we use bond bundle analysis to investigate the response of the charge density to an oriented electric field in general, and the catalytic effect of such a field on Diels-Alder reactions in particular, which in this case is found to catalyze by allowing the transition state valance bond bundle configuration to be achieved earlier along the reaction pathway. Using precise numerical values, we arrive at the conclusion that chemical reactions and electric field catalysis can be understood in terms of intra-atomic charge density redistribution, i.e., that charge shifts within more so than between atoms account for the making and breaking of bonds.

Download Full-text

Electron Charge Density Distribution from X-Ray Diffraction Study of the 4-Methoxybenzenecarbothioamide Compound

Journal of Crystallography ◽

10.1155/2013/326457 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Mokhtaria Drissi ◽

Abdelkader Chouaih ◽

Youcef Megrouss ◽

Fodil Hamzaoui

Keyword(s):

Charge Transfer ◽

Hydrogen Bonds ◽

Density Distribution ◽

Charge Density ◽

Title Compound ◽

Atomic Charge ◽

Crystallographic Axis ◽

Electron Charge ◽

Charge Density Distribution ◽

Electron Charge Density

The molecular electron charge density distribution of the title compound is described accurately using the multipolar model of Hansen and Coppens. The net atomic charge and the in-crystal molecular dipole moment have been determined in order to understand the nature of inter- and intramolecular charge transfer. The study reveals the nature of intermolecular interactions including charge transfer and hydrogen bonds in the title compound. In this crystal, the molecules form dimers via N–HS intermolecular hydrogen bonds. The dimers are further linked by C–HO hydrogen bonds into chains along the c crystallographic axis. This study has also allowed us to determine the electrostatic potential and therefore locate the electropositive part and the electronegative part in molecular scale of the title compound.

Download Full-text

Monotonicity properties of the atomic charge density function

International Journal of Quantum Chemistry ◽

10.1002/(sici)1097-461x(1996)58:1<11::aid-qua2>3.0.co;2-0 ◽

1996 ◽

Vol 58 (1) ◽

pp. 11-21 ◽

Cited By ~ 7

Author(s):

J. C. Angulo ◽

R. J. Y��ez ◽

J. S. Dehesa ◽

E. Romera

Keyword(s):

Charge Density ◽

Density Function ◽

Atomic Charge ◽

Monotonicity Properties

Download Full-text

Probing the Internal Atomic Charge Density Distributions in Real Space

ACS Nano ◽

10.1021/acsnano.8b03712 ◽

2018 ◽

Vol 12 (9) ◽

pp. 8875-8881 ◽

Cited By ~ 10

Author(s):

Gabriel Sánchez-Santolino ◽

Nathan R. Lugg ◽

Takehito Seki ◽

Ryo Ishikawa ◽

Scott D. Findlay ◽

...

Keyword(s):

Charge Density ◽

Atomic Charge ◽

Real Space ◽

Density Distributions

Download Full-text

Antisymmetric features of atomic charge density: Their significance in studies of electron redistribution accompanying bonding, and their relevance to thegeneral problem of structure and properties of molecules

Australian Journal of Chemistry ◽

10.1071/ch9650595 ◽

1965 ◽

Vol 18 (5) ◽

pp. 595 ◽

Cited By ~ 5

Author(s):

B Dawson

Keyword(s):

Neutron Diffraction ◽

Charge Density ◽

Elevated Temperatures ◽

Covalent Bond ◽

Atomic Charge ◽

Electronic Charge ◽

Structure And Properties ◽

Hydrogen Atoms ◽

X Ray ◽

Molecular Systems

A discussion is given of aspects of atomic charge density which possess the property of antisymmetry about the reference nuclear centre. It is shown that components of electronic charge density displaying this property must be an integral part of all bonded atoms possessing non-centric environments. The significance of such components for detailed X-ray diffraction studies of the electron redistribution which characterizes covalent bond formation is demonstrated for the case of carbon in diamond, and it is shown that the so-called "forbidden" 222 reflexion there is a natural consequence of antisymmetric features required by the non-centric (tetrahedral) disposition of bonded atoms in this lattice. Detailed X-ray studies of anthracene, salicylic acid, and cyanuric acid are cited to illustrate the importance and generality of antisymmetry concepts in accurate examinations of molecular systems; their significance in explaining long-standing discrepancies in the location of hydrogen atoms by X-ray and neutron diffraction methods is also noted. The discussion also demonstrates the relevance of antisymmetry to recent important neutron diffraction studies of fluorite structures at different elevated temperatures. Here, the accessible aspects of atomic charge density are those of nuclear charge density, i.e. nuclear vibrational behaviour, and it is shown that the presence of significant anharmonicity in the anionic vibrational pattern is responsible for the unusual diffraction effects observed. This anharmonicity has the same antisymmetry characteristics as those responsible for the 222 reflexion observed in X-ray studies of diamond. It is predicted that .future neutron studies of diamond structures (C, Si, Ge) at elevated temperatures should reveal a range of "forbidden" reflexions produced by antisymmetric components in the nuclear motions about their equilibrium positions. The discussion concludes with brief comments on the multipolar nature of bonded atoms arising from antisymmetric components in their electronic charge densities. Preliminary remarks are made on the relevance of the multipole concept to general problems of structure and properties of molecular systems.

Download Full-text

Molecular charge density analysis

Canadian Journal of Chemistry ◽

10.1139/v96-117 ◽

1996 ◽

Vol 74 (6) ◽

pp. 1049-1053 ◽

Cited By ~ 2

Author(s):

Juergen Hinze ◽

F. Biegler-Konig ◽

A.G. Lowe

Keyword(s):

Wave Function ◽

Density Matrix ◽

Charge Density ◽

Goodness Of Fit ◽

Form Factors ◽

Atomic Charge ◽

First Order ◽

Molecular Charge ◽

Molecular Wave Function ◽

Reduced Density

It is proposed to analyse the first-order reduced density matrix of a molecular wave function in terms of the first-order reduced density matrices of different states of the constituent atoms. With this an unambiguous partitioning of the molecular charge distribution in terms of the atomic charge distributions is obtained. Simple practical formulae are derived, such that in many ab initio molecular wave function calculations the analysis proposed can be carried out routinely. The results obtained should be useful for the interpretation of molecular wave functions in terms of their atomic constituents, as well as for the determination of atomic form factors to be used in X-ray molecular structure determination. Some simple examples are given, and the results obtained are compared with those obtained using other methods of analysis. Key words: charge density, density matrix, goodness-of-fit, correlation coefficient, standard deviation.

Download Full-text