Correlation energy in triplet electronic states. Application of the many-body Rayleigh-Schrödinger perturbation theory in the restricted Roothaan-Hartree-Fock formalism

1981 ◽  
Vol 46 (6) ◽  
pp. 1324-1331 ◽  
Author(s):  
Petr Čársky ◽  
Ivan Hubač
Keyword(s):  
Wave Function ◽  
Perturbation Theory ◽  
Correlation Energy ◽  
Electronic States ◽  
Many Body ◽  
Third Order ◽  
Explicit Formulas ◽  
Hartree Fock ◽  
The Many ◽  
Schrödinger Perturbation

Explicit formulas over orbitals are given for the correlation energy in triplet electronic states of atoms and molecules. The formulas were obtained by means of the diagrammatic many-body Rayleigh-Schrodinger perturbation theory through third order assuming a single determinant restricted Roothaan-Hartree-Fock wave function. A numerical example is presented for the NH molecule.

scholarly journals THE METHOD OF INCREMENTS — A WAVEFUNCTION-BASED AB-INITIO CORRELATION METHOD FOR SOLIDS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2204-2214 ◽  
Author(s):  
BEATE PAULUS
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Ground State ◽  
Infinite System ◽  
Correlation Energy ◽  
Correlation Method ◽  
Many Body ◽  
Hartree Fock ◽  
The Many ◽  
Good Agreement

The method of increments is a wavefunction-based ab initio correlation method for solids, which explicitly calculates the many-body wavefunction of the system. After a Hartree-Fock treatment of the infinite system the correlation energy of the solid is expanded in terms of localised orbitals or of a group of localised orbitals. The method of increments has been applied to a great variety of materials with a band gap, but in this paper the extension to metals is described. The application to solid mercury is presented, where we achieve very good agreement of the calculated ground-state properties with the experimental data.

Ab initio calculations of the ground state potential function of the hydroxyl anion by means of the many-body Rayleigh-Schrödinger perturbation theory

1981 ◽  
Vol 46 (11) ◽  
pp. 2595-2599
Author(s):  
Ivan Kozák ◽  
Vladimír Špirko ◽  
Petr Čársky
Keyword(s):  
Perturbation Theory ◽  
Ground State ◽  
Negative Ions ◽  
Spectroscopic Constants ◽  
Many Body ◽  
Hydroxyl Anion ◽  
Wide Range ◽  
State Potential ◽  
The Many ◽  
Schrödinger Perturbation

Many-body Rayleigh-Schrödinger perturbation theory (MB-RSPT) up to third order applied to OH- in the range of interatomic distances from 0.0815 to 0.1175 nm. The energy data obtained are combined with the experimental RKR (ground state) potential of HF, and, a ground state potential of OH- is constructed (over a wide range of internuclear distances) within the framework of the reduced potential curve method. With the use of this potential the corresponding rotation-vibration Schrödinger equation is solved for 16OH-. The computed spectroscopic constants are compared with best reported calculations and available experimental evidence. The comparison indicates that MB-RSPT may be used as an adequate (and convenient) tool for the study of negative ions.

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