Validity of the perturbation theory for hard particle systems with very-short-range attraction

2002 ◽  
Vol 65 (3) ◽  
Author(s):  
Ph. Germain ◽  
S. Amokrane
Keyword(s):  
Perturbation Theory ◽  
Short Range ◽  
Particle Systems ◽  
Hard Particle

An Avoidance Model for Short-Range Order Induced by Soft Repulsions in Systems of Rigid Rods

1996 ◽  
Vol 463 ◽  
Author(s):  
Jining Han ◽  
Judith Herzfeld
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Mean Field ◽  
Axial Ratio ◽  
Field Approximation ◽  
Particle Systems ◽  
Range Order ◽  
Mean Field Approximation ◽  
Hard Particle ◽  
Rigid Rods

ABSTRACTThe effects of soft repulsions on hard particle systems are calculated using an avoidance model which improves upon the simple mean field approximation. The method not only yields a better free energy, but also gives an estimate for the short-range positional order induced by soft repulsions. The results indicate little short-range order for isotropically oriented rods. However, for parallel rods short-range order increases to significant levels as the particle axial ratio increases.

Diffusion processes in brownian particle systems with short-range interaction

1991 ◽  
Vol 74 (3) ◽  
pp. 649-664 ◽  
Author(s):  
Jörn Sonnenburg ◽  
Dietrich Kremp ◽  
Rainer Sändig
Keyword(s):  
Short Range ◽  
Diffusion Processes ◽  
Brownian Particle ◽  
Particle Systems ◽  
Short Range Interaction ◽  
Range Interaction

Perturbation theory of short-range atomic interactions

1970 ◽  
Vol 317 (1531) ◽  
pp. 545-574 ◽  
Keyword(s):  
Perturbation Theory ◽  
Short Range ◽  
Similarity Transformation ◽  
Order Theory ◽  
First Order ◽  
Hartree Fock ◽  
First Order Theory ◽  
Atomic Interactions ◽  
Cusp Conditions ◽  
Molecular Calculations

A new united atom perturbation theory of the interaction of two atoms at small separations is described. The key feature is a similarity transformation of the Schrödinger equation which enables the cusp conditions to be satisfied at both nuclei and preserves the correct molecular symmetry. The first-order theory is examined in detail and compared with other united atom theories. Numerical calculations are presented for the ground states of the systems H + 2 , HeH 2+ HeH, He 2 and Li + He, based mainly on Hartree-Fock wavefunctions for the united atoms, and are compared with accurate molecular calculations. The agreement is remarkably good for separations up to 1 bohr.

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