Size-consistent single-reference methods for electronic correlation: a unified formulation through intermediate hamiltonian theory

1997 ◽  
Vol 95 (5) ◽  
pp. 215 ◽  
Author(s):  
José Sánchez-Marín ◽  
Ignacio Nebot-Gil ◽  
Jean Paul Malrieu ◽  
Jean Louis Heully ◽  
Daniel Maynau
Keyword(s):  
Electronic Correlation ◽  
Hamiltonian Theory ◽  
Reference Methods

Size-consistent single-reference methods for electronic correlation: a unified formulation through intermediate hamiltonian theory

1996 ◽  
Vol 95 (5-6) ◽  
pp. 215-241 ◽  
Author(s):  
José Sánchez-Marín ◽  
Ignacio Nebot-Gil ◽  
Jean Paul Malrieu ◽  
Jean Louis Heully ◽  
Daniel Maynau
Keyword(s):  
Electronic Correlation ◽  
Hamiltonian Theory ◽  
Reference Methods

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>

Study of potential curves by UHF type methods. CH4 molecule and its dissociation products

1986 ◽  
Vol 51 (4) ◽  
pp. 731-737
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Quantum Chemistry ◽  
High Energy ◽  
Basis Set ◽  
Electronic Correlation ◽  
Exact Methods ◽  
Energy Parameters ◽  
Bond Functions ◽  
The Individual ◽  
Potential Curves

Geometry and energy parameters of the individual dissociation intermediate steps of CH4 molecule, parameters of the barrier to linearity and singlet-triplet separation of the CH2 molecule have been calculated by means of the UMP method in the minimum basis set augmented with the bond functions. The results agree well with experimental data except for the geometry of CH2(1A1) and relatively high energy values of CH(2II) and CH2(1A1) where the existence of two UHF solutions indicates a necessity of description of the electronic correlation by more exact methods of quantum chemistry.

scholarly journals Interplay between multipolar spin interactions, Jahn-Teller effect, and electronic correlation in a Jeff=32 insulator

2021 ◽  
Vol 103 (10) ◽  
Author(s):  
Dario Fiore Mosca ◽  
Leonid V. Pourovskii ◽  
Beom Hyun Kim ◽  
Peitao Liu ◽  
Samuele Sanna ◽  
...  
Keyword(s):  
Teller Effect ◽  
Electronic Correlation ◽  
Spin Interactions ◽  
Jahn Teller ◽  
Jahn Teller Effect

Vectorial measurements of speckle displacement by the 2-D electronic correlation method

1985 ◽  
Vol 24 (5) ◽  
pp. 660 ◽  
Author(s):  
Nobukatsu Takai ◽  
Toshimitsu Asakura
Keyword(s):  
Correlation Method ◽  
Electronic Correlation

Reference methods and their wider applicability to measurements of roundness profiles

1998 ◽  
Vol 115 (4) ◽  
pp. 197-202
Author(s):  
S. Adamczak ◽  
D. Janecki
Keyword(s):  
Reference Methods

The determination of energies and wavefunctions with full electronic correlation

1969 ◽  
Vol 310 (1500) ◽  
pp. 43-61 ◽  
Keyword(s):  
Correlation Function ◽  
Wave Equation ◽  
Variational Problems ◽  
Variation Theory ◽  
Electronic Correlation ◽  
Convergence Properties

It has been widely thought that the use of wavefunctions with full electronic correlation would involve integrals of 3 N dimensions, where N is the number of electrons. Here it is shown that by a method similar to that of variation theory a set of equations which determine the orbitals and correlation function can be derived so that they only involve integrals of up to nine dimensions. Even these nine-dimensional integrals have some special characteristics which make them equivalent to six-dimensional integrals in some methods of integration. The method is formulated for the particular canonical choice of correlation function that has been previously investigated by the authors and is based on a particular trans-correlated kind of wave equation and on some particular convergence properties recently shown for bi-variational problems. This appears to provide a solution to the problem of including all r ij - quantities in wavefunctions: a problem which has been variously discussed for the last thirty years.

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