Vibrational analyses of p-benzoquinodimethane and p-benzoquinone based on ab initio Hartree-Fock and second-order Moller-Plesset calculations

1995 ◽  
Vol 99 (21) ◽  
pp. 8524-8534 ◽  
Author(s):  
Yoshihiro Yamakita ◽  
Mitsuo Tasumi
Keyword(s):  
Ab Initio ◽  
Second Order ◽  
Hartree Fock ◽  
Moller Plesset

scholarly journals AB INITIO STUDY OF AMMONIA CLUSTERS: (NH3)n (n = 2-6)

2010 ◽  
Vol 8 (3) ◽  
pp. 392-396 ◽  
Author(s):  
Herudi Kandau ◽  
Hanggara Sudrajat ◽  
Andreas Napitupulu ◽  
Syahrul Khairi ◽  
Zaky Al-Fatony ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Ab Initio ◽  
Ab Initio Calculation ◽  
Dipole Moments ◽  
Second Order ◽  
Basis Sets ◽  
Hartree Fock ◽  
Moller Plesset ◽  
Ammonia Clusters ◽  
Hydrogen Bonded

Hydrogen bonded neutral clusters of ammonia, (NH3)n (n = 2-6), have been theoretically investigated employing the D95++(d,p) (and wherever necessary, higher) basis sets at the Hartree-Fock (HF) level as well as with second-order Møller-Plesset (MP2) perturbation theory. While the ammonia trimer and tetramer exhibit perfect molecular symmetries and are nonpolar, the pentamer and hexamer both optimize with slight deviations from perfect symmetries and are seen to posses marginal, but nonzero dipole moments. The (NH3)n linear clusters are seen to be chemically softer than the corresponding cyclic ones.   Keywords: ab initio calculation, ammonia clusters, Hartree-Fock, Møller-Plesset

Polaronic and Bipolaronic Enhancement of Second Hyperpolarizabilities in Dithienyl Polyenes from Ab Initio Quantum Methods

1999 ◽  
Vol 597 ◽  
Author(s):  
Steven Trohalaki ◽  
Robert J. Zellmer ◽  
Ruth Pachter
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Valence Bond ◽  
Closed Shell ◽  
Functional Theory ◽  
Molecular Conformations ◽  
Hartree Fock ◽  
Molecular Charge ◽  
Field Methodology ◽  
Moller Plesset

AbstractSpangler and He [1,2] have shown that dithienyl polyenes form extremely stable bipolaronic dications when oxidatively doped in solution. Previous theoretical studies applied empirical methods to predict bipolaronic enhancement of hyperpolarizabilities for simple polyenes [3,4]. Here, we employ density functional theory to optimize the gas-phase molecular conformations of neutral, cationic, and dicationic forms of a series of dithienyl polyenes, where the number of ethene units, N, is varied from 1–5. Ab initio Hartree-Fock, generalized valence bond, configuration interaction, and Møller-Plesset calculations demonstrate that the dications are farily well described with a closed shell and therefore have little biradicaloid character. Second hyperpolarizabilities, γ, are subsequently calculated using ab initio Hartree-Fock theory and a finite field methodology. As expected, γ increases with the number of ethene units for a given molecular charge. The cations also show the largest increase in γ with N. For a given value of N, the cations display the largest γ values. However, if we treat the dication as a triplet, which might be present in solution, then it displays the largest γ.

The 1,2,3,5-ditelluradiazolyl [HCN2Te2] species. Theoretical characterizations of the cation, radical, and radical dimers

1996 ◽  
Vol 74 (6) ◽  
pp. 810-818 ◽  
Author(s):  
William M. Davis ◽  
John D. Goddard
Keyword(s):  
Ab Initio ◽  
Electron Correlation ◽  
Cation Radical ◽  
Building Blocks ◽  
Molecular Conductors ◽  
Face To Face ◽  
Hartree Fock ◽  
Symmetry Constraints ◽  
Moller Plesset ◽  
Low Dimensional

Dithia- and diselena-diazolyl radicals (HCN2E2 E = S, Se) and dimers are important building blocks in the design of low-dimensional molecular conductors. Research on the tellurium-based analogues is much rarer. This work reports the molecular and electronic structures of the cation, radical, and radical dimers of 1,2,3,5-ditelluradiazolyl using ab initio theory including electron correlation by Møller–Plesset perturbation theory up to partial fourth order (MP4SDQ). A face-to-face C2v dimer is predicted to be bound with respect to two radicals by approximately 18 kcal/mol. A C2h, dimer also has been studied and is ca. 2 kcal/mol less stable than the C2v conformer. Relaxing symmetry constraints on the dimers led to more energetically stable structures at the Hartree–Fock level but the C2v structure remains the most stable at a level of theory including electron correlation effects. The results for the Te compounds along with our earlier research on the S and Se analogues provide predictions for the geometries, vibrational frequencies, and ionization potentials for the Te species to assist in future experiments. Key words: tellurium, ab initio, ditelluradiazolyl, dimers, binding.

Second-Order ab Initio Møller−Plesset Study of Optimum Chain Length for Total (Electronic Plus Vibrational) β(−ωσ;ω1,ω2) of a Prototype Push-Pull Polyene

2001 ◽  
Vol 105 (42) ◽  
pp. 9748-9755 ◽  
Author(s):  
Denis Jacquemin ◽  
Benoît Champagne ◽  
Eric A. Perpète ◽  
Josep M. Luis ◽  
Bernard Kirtman
Keyword(s):  
Ab Initio ◽  
Chain Length ◽  
Second Order ◽  
Moller Plesset
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