scholarly journals Variable van der Waals Radii Derived From a Hybrid Gaussian Charge Distribution Model for Continuum-Solvent Electrostatic Calculations

2016 ◽  
Vol 230 (5-7) ◽  
Author(s):  
Renlong Ye ◽  
Xuemei Nie ◽  
Chung F. Wong ◽  
Xuedong Gong ◽  
Yan A. Wang ◽  
...  
Keyword(s):  
Charge Distribution ◽  
Chem Phys ◽  
Molecular Surface ◽  
Distribution Model ◽  
Discrete Point ◽  
Gaussian Functions ◽  
Molecular Electron ◽  
Semi Empirical ◽  
Van Der Waals Radii ◽  
Electrostatic Calculations

AbstractWe introduce a hybrid Gaussian charge distribution model (HGM) that partitions the molecular electron density into overlapping spherical atomic domains. The semi-empirical HGM consists of atom-centered spherical Gaussian functions and discrete point charges, which are optimized to reproduce the electrostatic potential on the molecular surface as well as the number of electrons in atom-centered and certain off-atom-centered spherical regions as closely as possible. In contrast, our previous Gaussian charge distribution model [J. Chem. Phys.

Comment on “Surface-charge distribution on a dielectric sphere due to an external point charge: examples of C60 and C240 fullerenes, Phys. Chem. Chem. Phys., 2013, 15, 20115”

2014 ◽  
Vol 16 (28) ◽  
pp. 14969-14970
Author(s):  
Henning Zettergren ◽  
Fredrik Lindén ◽  
Henrik Cederquist
Keyword(s):  
Dielectric Properties ◽  
Surface Charge ◽  
Charge Distribution ◽  
Point Charge ◽  
Chem Phys ◽  
Dielectric Sphere ◽  
External Point ◽  
Surface Charge Distribution ◽  
Phys Chem Chem Phys

We show that the relative surface charge distribution from classical electrostatics cannot be used to discriminate between different assumptions about the dielectric properties of fullerenes interacting with external charges.

SCF-MO computational analysis of the geometric conformation and charge distribution in picric acid and alkali picrate salts

1996 ◽  
Vol 74 (1) ◽  
pp. 70-78 ◽  
Author(s):  
Zbigniew Zimpel ◽  
Barbara R. Nelson ◽  
John A. Weil
Keyword(s):  
Charge Distribution ◽  
Computational Analysis ◽  
Picric Acid ◽  
Minimum Energy ◽  
Mulliken Charge ◽  
Resonance Effects ◽  
Molecular Electron ◽  
Optimized Model ◽  
Atomic Coordinates ◽  
Density Results

SCF-MO computations were employed in a study of picric acid, the –1 picrate ion, and Li, Na, and K picrates. Atomic coordinates from crystallographic structural analyses were used as initial parameters in the computation of the minimum-energy conformations of each free molecule at the 6-31G level. The Mulliken charge numbers for each atom in the optimized model molecules were calculated at the 6-31G** level. The induction and resonance effects of the OX group (X = H, Li, Na, K) on the trinitrophenyl ring are discussed. It is demonstrated that molecular (electron) isodensity surfaces (MIDCOs) describe charge-density results nicely compatible with the point Mulliken charge numbers. Key words: picrates, SCF-MO, charge distribution.

CALCULATION OF HO2 DENSITY OF STATES ON THREE POTENTIAL ENERGY SURFACES

2010 ◽  
Vol 09 (03) ◽  
pp. 653-665 ◽  
Author(s):  
H. ZHANG ◽  
S. C. SMITH
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Density Of States ◽  
Potential Energy Surfaces ◽  
Chem Phys ◽  
Many Body ◽  
Filter Diagonalization ◽  
Harmonic Density ◽  
Energy Surfaces ◽  
Semi Empirical

Density of states (DOS) in both bound and unimolecular dissociation regime for HO2 system have been calculated quantum mechanically by Lanczos homogeneous filter diagonalization (LHFD) method. Three potential energy surfaces are explored and the results are contrasted for the total angular momentum J = 0 density of states. While two ab initio potential energy surfaces (PESs) (TU PES, J Chem Phys, 115:3621 and XXZLG PES, J Chem Phys122:244) produce the DOSs which are in fairly good agreement, the semi-empirical double many-body expansion (DMBE) IV PES (J Phys Chem94:8073) generates the much higher DOSs in higher energy range. The quantum mechanical DOSs are also compared with Troe et al.'s results from harmonic density, semiclassical density and their early density of states on the same TU ab initio surface.

scholarly journals Effects of fluoro substitution on 4-bromodiphenyl ether (PBDE 3)

2008 ◽  
Vol 64 (1) ◽  
pp. 108-119 ◽  
Author(s):  
J. Klösener ◽  
D. C. Swenson ◽  
L. W. Robertson ◽  
G. Luthe
Keyword(s):  
Biological Effects ◽  
Diphenyl Ether ◽  
Environmental Pollutants ◽  
Torsion Angles ◽  
Bond Lengths ◽  
Structure Activity ◽  
Self Consistent Field ◽  
Semi Empirical ◽  
Van Der Waals Radii ◽  
Persistent Environmental Pollutants

It is our hypothesis that fluoro substitution provides a powerful tool to modulate the desired characteristics and to increase the specificity of studies of structure–activity relationships. 4-Bromodiphenyl ether (PBDE 3) and its five corresponding monofluorinated analogues (F-PBDEs 3) have been synthesized and fully characterized (using 1H, 13C and 19F NMR spectroscopy, and mass spectrometry). The accurate structure from X-ray crystal analysis was compared with iterative calculations using semi-empirical self-consistent field molecular-orbital (SCF-MO) models. The compounds studied were 4-bromodiphenyl ether (PBDE 3), the 13C6-isotopically labeled PBDE 3 (13C6-PBDE 3) and 2-fluoro-4-bromodiphenyl ether (3-2F), 2′-fluoro-4-bromodiphenyl ether (3-2′F), 3-fluoro-4-bromodiphenyl ether (3-3F), 3′-fluoro-4-bromodiphenyl ether (3-3′F), and 4′-fluoro-4-bromodiphenyl ether (3-4′F). Solid-state intermolecular interactions for PBDE 3 and the F-PBDEs 3 isomers are dominated by weak C—H(F,Br)...π and C—H...F interactions. The C—F bond lengths varied between 1.347 (2) and 1.362 (2) Å, and the C4—Br bond length between 1.880 (3) and 1.904 (2) Å. These bond lengths are correlated with electron-density differences, as determined by 13C shifts, but not with the strength of the C—F couplings. The interior ring angles of ipso-fluoro substitution increased (121.9–124.0°) as a result of hyperconjugation, a phenomenon also predicted by the calculation models. An attraction between the vicinal fluoro and halo substituents (observed in fluoro substituted chlorobiphenyls) was not observed for the bromo substituted F-PBDEs. The influence of a fluoro substituent on the conformation was only observable in PBDEs with di-ortho substitution. Calculated and observed torsion angles showed a positive correlation with increasing van der Waals radii and/or the degree of substitution for mono- to tetra-fluoro, chloro, bromo and methyl substitutions in the ortho positions of diphenyl ether. These findings utilizing F-tagged analogues presented here may prove fundamental to the interpretation of the biological effects and toxicities of these persistent environmental pollutants.

scholarly journals MODIFIKASI DISTRIBUSI MUATAN BERDASARKAN DISTRIBUSI FERMI-DIRAC DAN APLIKASINYA PADA HUKUM GAUSS

2020 ◽  
Vol 9 (2) ◽  
Author(s):  
Yuant Tiandho ◽  
Okky Maryana ◽  
Fitri Afriani ◽  
Asep Saefullah ◽  
Indra Pardede
Keyword(s):  
Charge Distribution ◽  
Important Variable ◽  
Distribution Model ◽  
Computer Based Learning ◽  
Solid Objects ◽  
Proposed Model ◽  
Computer Based ◽  
Definition Of ◽  
A Charge ◽  
Gaussian Surface

Gauss's law is one of the fundamental laws of physics, especially in the study of electricity. One of the important variable to use Gauss's law is the ability to determine the enclosed charge by the Gaussian surface. Commonly, the definition of the charge distribution of an object is defined by piecewise continuous function. In this paper, a charge distribution model that can accommodate all regions is proposed. The model is constructed based on analogies with the Fermi-Dirac's distribution function. The proposed model contains an exponential function that is related to the radius of an object and is equipped with a parameter to avoid the appearance of a not physical curve. The charge distribution can be used to calculate the enclosed charge by the Gaussian surface and to determine its electrical field. Some of the cases reviewed were spherical solid objects and spherical concentric objects. When compared to the conventional charge distribution, the modified distribution is more straightforward, and it can reduce the computational process algorithm. Therefore this can be used to construct concise and simple computer-based learning media.

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