scholarly journals Improvement of the Gaussian Electrostatic Model by Separate Fitting of Coulomb and Exchange-Repulsion Densities and Implementation of a new Dispersion term

2021 ◽  
Author(s):  
Sehr Naseem-Khan ◽  
Jean-Philip Piquemal ◽  
G. Andres Cisneros
Keyword(s):  
Electrostatic Model ◽  
Exchange Repulsion ◽  
Dispersion Term

scholarly journals Improvement of the Gaussian Electrostatic Model by Separate Fitting of Coulomb and Exchange-Repulsion Densities and Implementation of a new Dispersion term

2021 ◽  
Author(s):  
Sehr Naseem-Khan ◽  
Jean-Philip Piquemal ◽  
G. Andrés Cisneros
Keyword(s):  
Charge Transfer ◽  
Ab Initio ◽  
Gas Phase ◽  
Intermolecular Interaction ◽  
Binding Energies ◽  
Electrostatic Model ◽  
Polarizable Force Fields ◽  
Density Fitting ◽  
Exchange Repulsion ◽  
Dispersion Term

The description of each separable contribution of the intermolecular interaction is a useful approach to develop polarizable force fields (polFF). The Gaussian Electrostatic Model (GEM) is based on this approach, coupled with the use of density fitting techniques. In this work, we present the implementation and testing of two improvements of GEM: the Coulomb and Exchange-Repulsion energies are now computed with separate frozen molecular densities, and a new dispersion formulation inspired by the SIBFA polFF, which has been implemented to describe the dispersion and charge–transfer interactions. Thanks to the combination of GEM characteristics and these new features, we demonstrate a better agreement of the computed structural and condensed properties for water with experimental results, as well as binding energies in the gas phase with the ab initio reference compared with the previous GEM* potential. This work provides further improvements to GEM and the items that remain to be improved, and the importance of the accurate reproduction for each separate contribution.

Effect of delocalization of nonbonding electron density on the stability of the M–Ccarbene bond in main group metal-imidazol-2-ylidene complexes: a computational and structural database study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Samuel Tetteh ◽  
Albert Ofori
Keyword(s):  
Electron Density ◽  
Lone Pair ◽  
Main Group ◽  
Binding Energies ◽  
Electrostatic Model ◽  
Group Metal ◽  
Main Group Metal ◽  
Structural Database ◽  
The Stability ◽  
Lone Pair Electrons

Abstract The M–Ccarbene bond in metal (M) complexes involving the imidazol-2-ylidene (Im) ligand has largely been described using the σ-donor only model with donation of σ electrons from the sp-hybridized orbital of the carbene carbon into vacant orbitals on the metal centre. Analyses of the M–Ccarbene bond in a series of group IA, IIA and IIIA main group metal complexes show that the M-Im interactions are mostly electrostatic with the M–Ccarbene bond distances greater than the sum of the respective covalent radii. Estimation of the binding energies of a series of metal hydride/fluoride/chloride imidazol-2-ylidene complexes revealed that the stability of the M–Ccarbene bond in these complexes is not always commensurate with the σ-only electrostatic model. Further natural bond orbital (NBO) analyses at the DFT/B3LYP level of theory revealed substantial covalency in the M–Ccarbene bond with minor delocalization of electron density from the lone pair electrons on the halide ligands into antibonding molecular orbitals on the Im ligand. Calculation of the thermodynamic stability of the M–Ccarbene bond showed that these interactions are mostly endothermic in the gas phase with reduced entropies giving an overall ΔG > 0.

Electronegativities of the elements from a nonempirical electrostatic model

1981 ◽  
Vol 75 (11) ◽  
pp. 5385-5388 ◽  
Author(s):  
Russell J. Boyd ◽  
George E. Markus
Keyword(s):  
Electrostatic Model

Analytical electrostatic model of silicon conical field emitters. I

2001 ◽  
Vol 48 (1) ◽  
pp. 134-143 ◽  
Author(s):  
L. Dvorson ◽  
Meng Ding ◽  
A.I. Akinwande
Keyword(s):  
Electrostatic Model ◽  
Field Emitters

Role of the electrostatic model in calculating rare-earth crystal-field parameters

1998 ◽  
Vol 275-277 ◽  
pp. 230-233 ◽  
Author(s):  
Sverker Edvardsson ◽  
Mattias Klintenberg
Keyword(s):  
Rare Earth ◽  
Crystal Field ◽  
Electrostatic Model ◽  
Crystal Field Parameters

The three-center electrostatic model of diatomic bonds

2005 ◽  
Vol 731 (1-3) ◽  
pp. 39-48
Author(s):  
Yang Pin
Keyword(s):  
Electrostatic Model

scholarly journals An electrostatic model for zeros of classical Laguerre polynomials perturbed by a rational factor

2014 ◽  
Vol 8 (2) ◽  
Author(s):  
Luis Alejandro Molano Molano
Keyword(s):  
Laguerre Polynomials ◽  
Electrostatic Model ◽  
Rational Factor

scholarly journals Plausible molecular mechanism for activation by fumarate and electron transfer of the dopamine β-mono-oxygenase reaction

2002 ◽  
Vol 367 (1) ◽  
pp. 77-85 ◽  
Author(s):  
D. Shyamali WIMALASENA ◽  
Samantha P. JAYATILLAKE ◽  
Donovan C. HAINES ◽  
Kandatege WIMALASENA
Keyword(s):  
Electron Transfer ◽  
Molecular Mechanism ◽  
Geometric Isomer ◽  
Enzyme Activation ◽  
Reduced Form ◽  
Electrostatic Model ◽  
Steady State Kinetic ◽  
Low Concentrations ◽  
Substrate Inhibitor ◽  
Inhibition Potency

A series of fumarate analogues has been used to explore the molecular mechanism of the activation of dopamine β-mono-oxygenase by fumarate. Mesaconic acid (MA) and trans-glutaconic acid (TGA) both activate the enzyme at low concentrations, similar to fumarate. However, unlike fumarate, TGA and MA interact effectively with the oxidized enzyme to inhibit it at concentrations of 1—5mM. Monoethylfumarate (EFum) does not activate the enzyme, but inhibits it. In contrast with TGA and MA, however, EFum inhibits the enzyme by interacting with the reduced form. The saturated dicarboxylic acid analogues, the geometric isomer and the diamide of fumaric acid do not either activate or inhibit the enzyme. The phenylethylamine—fumarate conjugate, N-(2-phenylethyl)fumaramide (PEA-Fum), is an 600-fold more potent inhibitor than EFum and behaves as a bi-substrate inhibitor for the reduced enzyme. The amide of PEA-Fum behaves similarly, but with an inhibition potency 20-fold less than that of PEA-Fum. The phenylethylamine conjugates of saturated or geometric isomers of fumarate do not inhibit the enzyme. Based on these findings and on steady-state kinetic analysis, an electrostatic model involving an interaction between the amine group of the enzyme-bound substrate and a carboxylate group of fumarate is proposed to account for enzyme activation by fumarate. Furthermore, in light of the recently proposed model for the similar copper enzyme, peptidylglycine α-hydroxylating mono-oxygenase, the above electrostatic model suggests that fumarate may also play a role in efficient electron transfer between the active-site copper centres of dopamine β-mono-oxygenase.

New electrostatic model for the calculation of the energies for the hydration of the univalent gaseous ions

1982 ◽  
Vol 86 (9) ◽  
pp. 1544-1551 ◽  
Author(s):  
B. Thimme Gowda ◽  
Sidney W. Benson
Keyword(s):  
Electrostatic Model
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