ISSN:
1572-8951
Keywords:
Separability
;
wavefunction factorization
;
additivity rules
;
LiCl dissociation
;
group functions
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The idea of 'separability' is concerned with the quantum mechanical description of systems in which it is possible to recognize experimentally the resence of certain 'structural units', each with a 'personal' identity. The aim of this paper is to account for the striking success of this model and to develop the mathematical tools for its refinement and exploitation. At the root of the concept of separability lies the possibility of factorizing the wave-function for the whole system into a product of factors, each of which refers to a constituent part – a certain 'group' of electrons. In this 'group function' approximation the wavefunction for the whole system is written as an antisymmetrized product of strong-orthogonal group functions, one for each subsystem. Although the resultant ansatz is well known, its deeper implications and full potential have never been fully explored. Progress has been made in several directions: these include the separation of charge, current and spin densities into subsystem contributions, which provides a basis for the discussion of 'additivity rules'; an extension of the formalism to admit relativistic effects, using both 2-component and 4-component (Dirac-type) spin-orbitals; and a practical implementation of a variational procedure which leads to an optimal separation of given form, whilst preserving strong-orthogonality of the subsystems. To illustrate the approach, the dissociation curve for the molecule LiCl has been calculated using a 'two-group' approximation in which 4 'valence electrons' (a bond pair and an electron pair) are separated from the remaining 16 'core electrons'. The bond-breaking process is well described and there appears to be much potential for using this approach in the study of chemical reactions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1008266011351
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