The Pair-Correlation Problem and the Coupled-Cluster Approach

  • Ingvar Lindgren
  • John Morrison
Part of the Springer Series in Chemical Physics book series (CHEMICAL, volume 13)

Abstract

In the Chapters 12 and 13 we have seen how the electron correlation can be treated order by order for closed-shell and open-shell systems, respectively. It is quite obvious, however, that this approach rapidly gets very cumbersome, and —at least for open-shell systems—it is hardly feasible to go beyond the third-order energy in this way. As demonstrated in Chap. 13, higher-order terms can have quite an appreciable effect on quantities like the term splitting. Therefore, it would be highly desirable to find a more practical way of evaluating higher-order contributions. In the present chapter we shall develop such a procedure, which is based on the solution of a system of coupled differential equations of the type considered in Sect. 13.5. By considering one- and two-particle equations, it is possible to treat the dominating correlation effect, namely the pair correlation, in a complete way. This appears to be a very promising approach for an accurate treatment of the electron correlation for atomic and molecular systems.

Keywords

Helium Kelly Beryllium Neon Nonin 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1982

Authors and Affiliations

  • Ingvar Lindgren
    • 1
  • John Morrison
    • 1
  1. 1.Department of PhysicsChalmers University or TechnologyGöteborgSweden

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