Energy decomposition based on the extended virial theorem: Hartree-Fock and second-order Møller-Plesset results

2008 ◽  
Vol 109 (11) ◽  
pp. 2599-2605 ◽  
Author(s):  
Gyula Tasi ◽  
Dóra Barna
Keyword(s):  
Virial Theorem ◽  
Second Order ◽  
Energy Decomposition ◽  
Hartree Fock ◽  
Moller Plesset

scholarly journals Second Harmonic Generation, Electrooptical Pockels Effect, and Static First-Order Hyperpolarizabilities of 2,2′-Bithiophene Conformers: An HF, MP2, and DFT Theoretical Investigation

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Andrea Alparone
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Density Functional ◽  
Second Harmonic ◽  
Second Order ◽  
Pockels Effect ◽  
First Order ◽  
Hartree Fock ◽  
Electron Correlation Effects ◽  
Moller Plesset

The static and dynamic electronic (hyper)polarizabilities of the equilibrium conformations of 2,2′-bithiophene (anti-gauche and syn-gauche) were computed in the gas phase. The calculations were carried out using Hartree-Fock (HF), Møller-Plesset second-order perturbation theory (MP2), and density functional theory methods. The properties were evaluated for the second harmonic generation (SHG), and electrooptical Pockels effect (EOPE) nonlinear optical processes at the typical λ=1064 nm of the Nd:YAG laser. The anti-gauche form characterized by the S–C2–C2′–S dihedral angle of 137° (MP2/6-311G**) is the global minimum on the potential energy surface, whereas the syn-gauche rotamer (S–C2–C2′–S = 48°, MP2/6-311G**) lies ca. 0.5 kcal/mol above the anti-gauche form. The structural properties of the gauche structures are rather similar to each other. The MP2 electron correlation effects are dramatic for the first-order hyperpolarizabilities of the 2,2′-bithiophenes, decreasing the HF values by ca. a factor of three. When passing from the anti-gauche to the syn-gauche conformer, the static and frequency-dependent first-order hyperpolarizabilities increase by ca. a factor of two. Differently, the electronic polarizabilities and second-order hyperpolarizabilities of these rotamers are rather close to each other. The syn-gauche structure could be discriminated from the anti-gauche one through its much more intense SHG and EOPE signals.

A quantum approach to the mechanism of electrochemical reductions

1986 ◽  
Vol 64 (12) ◽  
pp. 2359-2364 ◽  
Author(s):  
Juan J. Novoa
Keyword(s):  
Total Energy ◽  
Electrochemical Reduction ◽  
Second Order ◽  
Basis Sets ◽  
Hartree Fock ◽  
Quantum Approach ◽  
Moller Plesset

Using the Hartree–Fock method and, in some cases, the second order Moller–Plesset perturbational method, with 4-31G, 4-31 + G, and 4-31 + G* basis sets, a first approach to the study of the mechanism of electrochemical reduction from formaldehyde to ethanol is presented. The total energy and optimized geometry of each of the molecules involved are also given. A proton–electron–proton–electron type mechanism is proposed.

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