Valence-electron correlation in extended systems: A nonparametric exponential transformation of molecular orbitals into valence-bond wave functions

1991 ◽  
Vol 44 (4) ◽  
pp. 1480-1486 ◽  
Author(s):  
Brahim Oujia ◽  
Jean-Paul Malrieu
Keyword(s):  
Electron Correlation ◽  
Valence Electron ◽  
Valence Bond ◽  
Molecular Orbitals ◽  
Wave Functions ◽  
Exponential Transformation ◽  
Extended Systems

From one-electron to correlated wave functions in extended systems: A valence-bond investigation

1989 ◽  
Vol 39 (7) ◽  
pp. 3274-3288 ◽  
Author(s):  
Marie-Bernadette Lepetit ◽  
Brahim Oujia ◽  
Jean-Paul Malrieu ◽  
Daniel Maynau
Keyword(s):  
Valence Bond ◽  
Wave Functions ◽  
Extended Systems

Configurational interaction in molecular orbital theory. A higher approximation in the non-empirical method

1950 ◽  
Vol 200 (1063) ◽  
pp. 474-486 ◽  
Keyword(s):  
Valence Bond ◽  
Empirical Method ◽  
Molecular Orbitals ◽  
Wave Functions ◽  
Empirical Methods ◽  
Orbital Theory ◽  
Configurational Interaction ◽  
Spectral Bands ◽  
Bond Theory ◽  
Numerical Precision

The disagreements between calculations of the benzene energy states by the method of antisymmetric molecular orbitals (A. S. M. O.) and by the augmented valence-bond theory given in previous papers (Craig 1950 a to c ) are due, at least in part, to the neglect in the former of interaction between different ‘configurations’. Every scheme of assigning electrons to molecular orbitals is a configuration, and where states with different configurations have the same symmetry they interact with one another under the influence of electron repulsion and suffer energy changes. In this paper a study of these energy changes is made, using a limited set of configurations. The A. S. M. O. states are affected by amounts up to 5 eV, and this is enough to show that the A. S. M. O. theory cannot be used for the detailed understanding of molecular spectral bands. The inclusion of configurational interaction gives the next higher approximation and makes the method, in principle, as general as is compatible with the initial use of 2 p atomic wave functions. The method ought to prove valuable for settling in a non-empirical way issues for which the correctness of the simple empirical methods is in doubt. Even in the improved theory, however, the numerical precision required to interpret spectral separations in the order of 1 eV will be difficult to attain without the use of three-centre integrals and some other refinements.

scholarly journals Resonating Valence Bond Wave Functions for Strongly Frustrated Spin Systems

2001 ◽  
Vol 87 (9) ◽  
Author(s):  
Luca Capriotti ◽  
Federico Becca ◽  
Alberto Parola ◽  
Sandro Sorella
Keyword(s):  
Valence Bond ◽  
Spin Systems ◽  
Wave Functions ◽  
Resonating Valence Bond ◽  
Frustrated Spin

Excitation Energies from a Partially Spin-Restricted Wave Function

2007 ◽  
Vol 3 (1) ◽  
pp. 65-69 ◽  
Author(s):  
V.N. Glushkov
Keyword(s):  
Wave Function ◽  
Excited States ◽  
Electron Correlation ◽  
Electronic Excitation ◽  
Slater Determinant ◽  
Molecular Orbitals ◽  
Reference Configuration ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Natural Base

A singe Slater determinant consisting of restricted and unrestricted, in spins, parts is proposed to construct a reference configuration for singlet excited states having the same symmetry as the ground one. A partially restricted Hartree-Fock approach is developed to derive amended equations determining the spatial molecular orbitals for singlet excited states. They present the natural base to describe the electron correlation in excited states using the wellestablished spin-annihilated perturbation theories. The efficiency of the proposed method is demonstrated by calculations of electronic excitation energies for the Be atom and LiH molecule.

Exponential transformation of molecular orbitals

1994 ◽  
Vol 101 (5) ◽  
pp. 3862-3865 ◽  
Author(s):  
Jürg Hutter ◽  
Michele Parrinello ◽  
Stefan Vogel
Keyword(s):  
Molecular Orbitals ◽  
Exponential Transformation
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