Semi-empirical MO study of refractions modelling biochemical oxidation of ethanol

1983 ◽  
Vol 48 (2) ◽  
pp. 484-503
Author(s):  
Jiří Krechl ◽  
Josef Kuthan
Keyword(s):  
Quantum Chemical ◽  
Wave Functions ◽  
Chemical Characteristics ◽  
Biochemical Reactions ◽  
Biochemical Oxidation ◽  
Gradient Optimization ◽  
Semi Empirical ◽  
Protonated Acetaldehyde ◽  
Oxidation Of Ethanol

The EHT, CNDO/2 and INDO methods have been used to find the energetically most favourable arrangement of the supermolecules 1-methylnicotiniumamide cation (I - ethanol (II),I - ethoxide anion (III) and 1-methyl-1,4-dihydronicotinamide (IV) - protonated acetaldehyde (V). An attempt has been made to define with more precision these geometries with the use of the gradient optimization based on CNDO/2 wave functions. Quantum-chemical characteristics of the studied systems are discussed with respect to possible course of biochemical reactions.

Semi-empirical Molecular Orbital Energy Levels of the Hexammine and Chloroammine Complexes of Co(IV)

1967 ◽  
Vol 22 (2) ◽  
pp. 170-175 ◽  
Author(s):  
Walter A. Yeranos ◽  
David A. Hasman
Keyword(s):  
Molecular Orbital ◽  
Energy Levels ◽  
Empirical Evaluation ◽  
Wave Functions ◽  
Electronic Transitions ◽  
Orbital Energy ◽  
Molecular Orbital Energy ◽  
The One ◽  
Semi Empirical

Using the recently proposed reciprocal mean for the semi-empirical evaluation of resonance integrals, as well as approximate SCF wave functions for Co3+, the one-electron molecular energy levels of Co (NH3) 3+, Co (NH3) 5Cl2+, and Co (NH3) 4Cl21+ have been redetermined within the WOLFSBERG–HELMHOLZ approximation. The outcome of the study fits remarkably well with the observed electronic transitions in the u.v. spectra of these complexes and prompts different band assignments than previously suggested.

QSPR Analysis of Phenylthio Phenylsulfinyl and Phenylsulfonyl Esters Using Quantum Chemical Semi-Empirical Descriptors

2002 ◽  
Vol 49 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Chunsheng Yin ◽  
Shushen Liu ◽  
Hongxia Yu ◽  
Liansheng Wang
Keyword(s):  
Quantum Chemical ◽  
Semi Empirical

Анализ вычислительных и экспериментальных исследований переключения поляризации в ПВДФ и П (ВДФ-ТрФЭ) сегнетоэлектрических пленках на наноуровне

2015 ◽  
Vol 10 (2) ◽  
pp. 372-386 ◽  
Author(s):  
В.С. Быстров ◽  
V.S. Bystrov
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Electric Field ◽  
Quantum Chemical ◽  
Polyvinylidene Fluoride ◽  
Domain Switching ◽  
Polarization Switching ◽  
Molecular Structures ◽  
Switching Mechanism ◽  
Semi Empirical

In this paper, molecular models are used to investigate and analyze the polarization switching in the polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) Langmuir-Blodgett (LB) nanofilms, in comparison with the experimental data at the nanoscale. Quantum-mechanical calculations and modeling, as well as molecular dynamics (MD) simulations based on semi-empirical quantum-chemical methods (such as PM3), show that the energy of the studied PVDF and P (VDF-TrFE) molecular structures, and their polarization switching proceed by the intrinsic homogeneous switching mechanism in the framework of the phenomenological theory of Landau-Ginzburg-Devonshire (LGD) in the linear approximation at low values of the electric field. The magnitude of the resulting critical coercive field is within the EC ~ 0.5 ... 2.5 GV/m, which is consistent with experimental data. It is also found that the uniform polarization switching mechanism of the polymer chains PVDF and P (VDF-TrFE) is due to the quantum properties of the molecular orbitals of the electron subsystem. This is clearly seen in both the polarization hysteresis loops, and the total energy changes. In this case, the turnover chain time, obtained by molecular dynamics within semi-empirical quantum-chemical PM3 approach in a limited Hartree-Fock approximation, when approaching this critical point, increases sharply, tending to infinity, which corresponds to the theory of LGD. Otherwise, at the high values of the applied electric field the polarization switching correspond to the extrinsic domain mechanism in the frame of the microscopic Kolmogorov–Avrami–Ishibashi (KAI) theory, describing bulk ferroelectric crystals and thick films. The performed analysis of computational and experimental data allows us to estimate the critical sizes of the possible transition region approximately on the order of 10 nm between intrinsic homogeneous and extrinsic domain switching mechanisms.

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