Theoretica chimica acta

, Volume 83, Issue 1, pp 69–103

Orthogonally spin-adapted multi-reference Hilbert space coupled-cluster formalism: diagrammatic formulation

  • Piotr Piecuch
  • Josef Paldus
Article

DOI: 10.1007/BF01113244

Cite this article as:
Piecuch, P. & Paldus, J. Theoret. Chim. Acta (1992) 83: 69. doi:10.1007/BF01113244

Summary

The problem of spin-adaptation of the multi-reference (MR) coupled-cluster (CC) formalism, employing Jeziorski-Monkhorst ansatz, is addressed. The diagrammatic technique based on graphical methods of spin algebras is generalized to the MR case, so that both direct and coupling terms can be determined. Usefulness of this fully diagrammatic spin-adaptation approach is illustrated on a derivation of explicit expressions for the linear and bilinear coupling terms that are required in the special two-reference MR-CC theory involving singly and doubly excited states (MR-CCSD formalism). Results obtained with the diagrammatic approach are compared with those derived earlier using the algebraic technique and relative advantages of both procedures are compared.

Key words

Many-electron correlation problemCoupled-cluster approachMulti-reference formalismSpin-adaptationGraphical methods of spin algebras

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Piotr Piecuch
    • 1
  • Josef Paldus
    • 1
    • 3
  1. 1.Department of Applied MathematicsUniversity of WaterlooWaterlooCanada
  2. 2.Institute of ChemistryUniversity of WroclawWroclawPoland
  3. 3.the Department of Chemistry, and Guelph-Waterloo Center for Graduate Work in Chemistry, Waterloo CampusUniversity of WaterlooWaterlooCanada