Cusped-Gaussian molecular wavefunctions. Part 5.—Basis sets for the second-row atoms

1987 ◽  
Vol 83 (5) ◽  
pp. 783-790 ◽  
Author(s):  
Erich Steiner
Keyword(s):  
Basis Sets ◽  
Molecular Wavefunctions

Gaussian basis sets for molecular wavefunctions containing third-row atoms

1971 ◽  
Vol 20 (1) ◽  
pp. 1-11 ◽  
Author(s):  
B. Roos ◽  
A. Veillard ◽  
G. Vinot
Keyword(s):  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Molecular Wavefunctions

Die Verwendung reiner Gauß-Basis-Funktionen zur Beschreibung der Elektronenbeugung an Gasmolekülen unter Berücksichtigung der chemischen Bindung / The Use of Gauss-Lobe-Functions for Calculating the Electron Diffraction Intensity from Gas Molecules under Consideration of Chemical Bond

1974 ◽  
Vol 29 (7) ◽  
pp. 1023-1033 ◽  
Author(s):  
Armin Haberl ◽  
Joachim Haase
Keyword(s):  
Electron Diffraction ◽  
Chemical Bond ◽  
Electron Scattering ◽  
Basis Sets ◽  
Molecular Vibration ◽  
Inelastic Electron ◽  
Diffraction Intensity ◽  
Analytic Expressions ◽  
Gas Molecules ◽  
Molecular Wavefunctions

The first Born Expression of elastic and inelastic electron scattering from gas molecules of any svmmetry leads to simple analytic expressions if molecular wavefunctions expanded in Gauss-Lobefunctions (GL's) are used and if the effect of molecular vibration is neglected. The result is given and in the case of H2O theoretical intensities are calculated from two HF-wavefunctions with medium sized GL-basis sets [ (5s, 3p/3s,-) and (5s, 4p/5s,-)] and compared with Konaka's experiment.

Electronegativity Equalization and the Deformation of Atomic Orbitals in Molecular Wavefunctions

1988 ◽  
Vol 41 (6) ◽  
pp. 827 ◽  
Author(s):  
E Magnusson
Keyword(s):  
Hydrogen Atom ◽  
Bond Distance ◽  
Basis Sets ◽  
Radial Dependence ◽  
Electronic Charge ◽  
Atomic Orbitals ◽  
Electronegativity Equalization ◽  
Electronegativity Difference ◽  
The Mean ◽  
Molecular Wavefunctions

Electronegativity equalization, which must accompany the formation of a chemical bond, occurs when electronic charge is transferred between the bound atoms but also by changes in the radial dependence of the atomic orbitals involved in the bonding. The degree of contraction or expansion of the atomic orbitals may be studied by analysing ab initio MO wavefunctions calculated with flexible basis sets. The effects on the hydrogen orbital are marked, the 1sHmean radius being progressively reduced by 9-23% across the series of first row hydrides (BH3 to HF) from its value in the hydrogen atom. The mean radius of the carbon 2p function in the wavefunctions of substituted methanes (CH3BH2 to CH3F) is correspondingly reduced by 2-19% from its free-atom value. Orbital contraction (or expansion) is dependent on bond distance, on the electronegativity difference of the bound atoms, and, because it varies from one MO to another, on the nature of the MO'S. The effects are greatest in MO'S which are strongly bonding.

Experimental and Theoretical (ab initio and DFT) Analysis of UV-Vis Spectra, Thermodynamic Functions and Non-linear Optical Properties of 2-Chloro-3,4-Dimethoxybenzaldehyde

2015 ◽  
Vol 8 (2) ◽  
pp. 2122-2134
Author(s):  
Sarvendra Kumar ◽  
Rajesh Kumar ◽  
Jayant Teotia ◽  
M. K. Yadav
Keyword(s):  
Thermodynamic Functions ◽  
Title Compound ◽  
Density Functional ◽  
Structural Characteristics ◽  
Basis Sets ◽  
Ultraviolet Absorption Spectrum ◽  
Non Linear ◽  
Different Temperatures ◽  
Linear Optical Properties ◽  
Linear Optical

In the present work, UV- Visible spectra of 2-Chloro-3,4-Dimethoxybenzaldehyde (2,3,4-CDMB) compound  have been carried out experimentally and theoretically. The ultraviolet absorption spectrum of title compound in three solvents (Acetone, Diethyl Ether, CCl4) of different polarity were examined in the range of 200–500 nm. The structure of the molecule was optimized and the structural characteristics were determined by HF and DFT (B3LYP) methods with 6-31+G(d,p) and 6-311++G(d,p) as basis sets. The excitation energy, wavelength corresponds to absorption maxima () and oscillator strength (f) are calculated by Time-Dependent Density Functional Theory (TD-DFT) using B3LYP/6-31+G(d,p) and B3LYP/6-311++G(d,p) as basis sets. The electric dipole moment (μ), polarizability (α) and the first hyperpolarizability (β ) have been computed to evaluate the non-linear optical (NLO) response of the investigated compound by HF and DFT (B3LYP) with already mentioned basis sets. Thermodynamic functions of the title compound at different temperatures were also calculated.

Electronic Structure Benchmark Calculations of Inorganic and Biochemical Carboxylation Reactions

2018 ◽  
Author(s):  
Oscar A. Douglas-Gallardo ◽  
David A. Sáez ◽  
Stefan Vogt-Geisse ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Electronic Structure ◽  
Chemical Reactions ◽  
Density Functional ◽  
Correlation Energy ◽  
Electronic Energy ◽  
Basis Sets ◽  
Electronic Correlation ◽  
Correct Description ◽  
Carbon Dioxide Co2 ◽  
High Level

<div><div><div><p>Carboxylation reactions represent a very special class of chemical reactions that is characterized by the presence of a carbon dioxide (CO2) molecule as reactive species within its global chemical equation. These reactions work as fundamental gear to accomplish the CO2 fixation and thus to build up more complex molecules through different technological and biochemical processes. In this context, a correct description of the CO2 electronic structure turns out to be crucial to study the chemical and electronic properties associated with this kind of reactions. Here, a sys- tematic study of CO2 electronic structure and its contribution to different carboxylation reaction electronic energies has been carried out by means of several high-level ab-initio post-Hartree Fock (post-HF) and Density Functional Theory (DFT) calculations for a set of biochemistry and inorganic systems. We have found that for a correct description of the CO2 electronic correlation energy it is necessary to include post-CCSD(T) contributions (beyond the gold standard). These high-order excitations are required to properly describe the interactions of the four π-electrons as- sociated with the two degenerated π-molecular orbitals of the CO2 molecule. Likewise, our results show that in some reactions it is possible to obtain accurate reaction electronic energy values with computationally less demanding methods when the error in the electronic correlation energy com- pensates between reactants and products. Furthermore, the provided post-HF reference values allowed to validate different DFT exchange-correlation functionals combined with different basis sets for chemical reactions that are relevant in biochemical CO2 fixing enzymes.</p></div></div></div>

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