Comparison of Fundamental and Harmonic Frequencies of First-Row Closed-Shell Diatomics Calculated Using Full ab Initio Methods and Composite Methods

2004 ◽  
Vol 108 (10) ◽  
pp. 1826-1829 ◽  
Author(s):  
Ryan P. A. Bettens
Keyword(s):  
Ab Initio ◽  
Closed Shell ◽  
Ab Initio Methods ◽  
Harmonic Frequencies ◽  
Composite Methods

The Smallest “Aurophilic Species”

2009 ◽  
Vol 64 (4) ◽  
pp. 388-394 ◽  
Author(s):  
Raphael J. F. Berger
Keyword(s):  
Ab Initio ◽  
Molecular Species ◽  
Structural Parameters ◽  
Relativistic Effects ◽  
Closed Shell ◽  
Basis Sets ◽  
Ab Initio Methods ◽  
Relativistic Treatment ◽  
Highly Correlated ◽  
Formation Energies

The existence of the C2v symmetric closed-shell di[gold(I)]hydronium cation [Au2H]+ (1), is predicted. It is shown that 1 is the smallest possible molecular species containing aurophilic contacts. Equilibrium structural parameters, vibrational frequencies and formation energies of 1 from Au+ and AuH, have been calculated, employing a series of highly correlated but available standard relativistic ab initio methods up to CCSD(T) level of theory and all-electron basis sets of quadruple-ζ quality with double polarizations. Relativistic effects have been taken into account by employing pseudorelativistic electron core potentials (ECP) or a scalar relativistic treatment using a Douglas-Kroll-Heß Hamiltonian of 2nd, 3rd and 4th order (DKH2, DKH3, DKH4).

Determination of acidic dissociation constants of L-phenylalanyl-glycine and L-alanyl-L-alanine in water using ab initio methods

2014 ◽  
Vol 2 (42) ◽  
pp. 263-263
Author(s):  
Farhoush Kiani ◽  
Mahmoud Tajbakhsh ◽  
Fereydoon Ashrafi ◽  
Nesa Shafiei ◽  
Azar Bahadori ◽  
...  
Keyword(s):  
Ab Initio ◽  
Dissociation Constants ◽  
Ab Initio Methods ◽  
Acidic Dissociation

Study of the structure and stability of aqua ions La(H2O) n 3+ (n = 8, 9) by ab initio methods

2008 ◽  
Vol 53 (8) ◽  
pp. 1249-1255 ◽  
Author(s):  
V. Yu. Buz’ko ◽  
I. V. Sukhno ◽  
M. B. Buz’ko ◽  
A. A. Polushin ◽  
V. T. Panyushkin
Keyword(s):  
Ab Initio ◽  
Ab Initio Methods ◽  
Structure And Stability

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.

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