Electrostatic potential in crystals of α-boron, γ-boron and boron carbide

2018 ◽  
Vol 233 (9-10) ◽  
pp. 663-673
Author(s):  
Christian B. Hübschle ◽  
Sander van Smaalen
Keyword(s):  
Boron Carbide ◽  
Electrostatic Potential ◽  
Chemical Bonds ◽  
Charge Densities ◽  
Icosahedral Cluster ◽  
Hirshfeld Surfaces ◽  
Infinite Network ◽  
Dynamic Charge ◽  
Extended Solids ◽  
Bonding Characteristics

Abstract An overview is given of the recently proposed method for computation of the electrostatic potential (ESP) of dynamic charge densities derived from multipole models [C. B. Hubschle, S. van Smaalen, J. Appl. Crystallogr. 2017, 50, 1627]. The dynamic ESP is presented for the multipole models of the boron polymorphs α-B12 and γ-B28, and stoichiometric boron carbide B13C2. Minimum values of the ESP are conspiciously equal at approximately −1 electron/Å. Regions with the ESP close to its minimum value form an extended network throughout the crystal structures at locations far away from atoms and bonds. Boron and boron carbide are extended solids containing an infinite network of strong chemical bonds. We have shown that for such solids, the ESP can usefully considered on Hirshfeld surfaces encompassing groups of atoms. Accordingly, we discuss bonding in boron and boron carbide with aid of the ESP on the Hirsfeld surface encompassing a B12 icosahedral cluster. The structure of the ESP corroborates the interpretation of the bonding characteristics previously proposed for α-B12, γ-B28 and B13C2.

scholarly journals The electrostatic potential of dynamic charge densities

2017 ◽  
Vol 50 (6) ◽  
pp. 1627-1636 ◽  
Author(s):  
Christian B. Hübschle ◽  
Sander van Smaalen
Keyword(s):  
Charge Density ◽  
Maximum Entropy ◽  
Single Molecule ◽  
Electrostatic Potential ◽  
Zero Point ◽  
Summation Method ◽  
Molecular Surface ◽  
Total Charge ◽  
Charge Densities ◽  
Dynamic Charge

A procedure to derive the electrostatic potential (ESP) for dynamic charge densities obtained from structure models or maximum-entropy densities is introduced. The ESP essentially is obtained by inverse Fourier transform of the dynamic structure factors of the total charge density corresponding to the independent atom model, the multipole model or maximum-entropy densities, employing dedicated software that will be part of theBayMEMsoftware package. Our approach is also discussed with respect to the Ewald summation method. It is argued that a meaningful ESP can only be obtained if identical thermal smearing is applied to the nuclear (positive) and electronic (negative) parts of the dynamic charge densities. The method is applied to structure models of DL-serine at three different temperatures of 20, 100 and 298 K. The ESP at locations near the atomic nuclei exhibits a drastic reduction with increasing temperature, the largest difference between the ESP from the static charge density and the ESP of the dynamic charge density being atT= 20 K. These features demonstrate that zero-point vibrations are sufficient for changing the spiky nature of the ESP at the nuclei into finite values. On 0.5 e Å−3isosurfaces of the electron densities (taken as the molecular surface relevant to intermolecular interactions), the dynamic ESP is surprisingly similar at all temperatures, while the static ESP of a single molecule has a slightly larger range and is shifted towards positive potential values.

scholarly journals Electrostatic potential of dynamic charge densities

2016 ◽  
Vol 72 (a1) ◽  
pp. s86-s86
Author(s):  
Christian B. Hübschle ◽  
Sander van Smaalen
Keyword(s):  
Electrostatic Potential ◽  
Charge Densities ◽  
Dynamic Charge

scholarly journals First principle study of occupancy, bonding characteristics and alloying effect of Zr, Nb, V in bulk γ-Fe(C)

2020 ◽  
Vol 213 ◽  
pp. 01019
Author(s):  
Fei Liu ◽  
Shan Cong ◽  
Long Hao
Keyword(s):  
Solid Solution ◽  
Covalent Bond ◽  
Alloy Element ◽  
Chemical Bonds ◽  
Covalent Bonds ◽  
Binding Characteristics ◽  
Crystal Cell ◽  
Ionic Bonds ◽  
Crystal Cells ◽  
Bonding Characteristics

The total energy, binding characteristics, density of states, charge distribution and differential charge density of γ-Fe(C)-M crystal cells formed by solid solution of Zr, Nb and V in γ-Fe(C) were calculated by using the first-principles method. Thus, the mechanism of Zr, Nb, and V with γ-Fe(C) was investigated in this paper. The results show that Zr, Nb and V all preferentially replaced the Fe atoms which are at the top angle in γ-Fe(C). Crystal cell reaches its highest stability after V solid solution. Nb reaches after it, and Zr is relatively weak. In the γ-Fe(C)-Zr cell, Fe-Zr covalent bond and Zr-C ionic bond are the main chemical bonds. In the γ-Fe(C)-Nb and γ-Fe(C)-V cells, Fe-Nb and Fe-V covalent bonds are the main chemical bonds with a number of Nb-C and V-C ionic bonds. After solid solution, the electron cloud density around C atom changed little, while Fe atom changed obviously. The orbital electrons around Fe atoms in γFe(C)-V has maximal distribution, which means that the electrons delocalized most and most of the electrons are bonding. It is the main factor for the increase in the binding energy of crystal cell. The effects of Zr, Nb, V solution on austenitic stability are investigated by studying the influence of alloy element on γFe(C) electronic structure.

scholarly journals New developments in the BayMEM Suite

2014 ◽  
Vol 70 (a1) ◽  
pp. C103-C103
Author(s):  
Christian Hübschle ◽  
Sander van Smaalen
Keyword(s):  
Electrostatic Potential ◽  
Maximum Entropy Method ◽  
Dynamic Deformation ◽  
Entropy Method ◽  
Prior Density ◽  
New Developments ◽  
Deformation Density ◽  
File Formats ◽  
Modulated Structures ◽  
Dynamic Charge

The program suite BayMEM consists of the programs PRIOR, BayMEM and EDMA. It is intended to apply the Maximum Entropy Method (MEM) to ordinary and modulated structures[1]. The PRIOR program is intended to calculate the prior density for the MEM calculation, but it has been recently shown that it can be used to calculate the dynamic charge density from multipolar refinements[2] as well. As a new functionality it is now also possible to calculate the electrostatic potential from the dynamic deformation density by the method described by Steward and Spackman[3]. We will present a new MapConverter program which allows to convert electron density stored in different file formats into an other. It is also possible to rearrange and cut the density in such a way, that it is possible, to have clear view of one molecule, not obscured by its symmetry mates, in a molecular viewer like MoleCoolQt for example.

Calculation of electrostatic potentials from multipole charge densities

1993 ◽  
Vol 208 (2) ◽  
Author(s):  
Hendrik L. De Bondt ◽  
N. M. Blaton ◽  
O. M. Peeters ◽  
C. J. De Ranter
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Charge Density ◽  
Electrostatic Potential ◽  
Electron Distribution ◽  
Density Model ◽  
Slater Type ◽  
Single Crystal Diffraction ◽  
Charge Densities ◽  
Resolution Single

AbstractA rigorous analytical expression is derived for the electrostatic potential originating from aspherical atomic multipole electron densities according to the Stewart or Hansen-Coppens charge density model with a Slater type radial electron distribution. Such models are widely used to determine charge distributions from high resolution single crystal diffraction experiments.

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