https://doi.org/10.1140/epjd/e2002-00103-6
A multi-reference exponential expansion for the electronic wave function
Laboratoire de Physique Quantique (UMR 5626 du CNRS) ,
Université Paul Sabatier,
118 route de Narbonne,
31062 Toulouse Cedex, France and
Dipartimento di Chimica Fisica e Inorganica,
Università di Bologna,
Viale Risorgimento 4, 40136 Bologna, Italy
Corresponding author: a stefano@irsamc1.ups-tlse.fr
Received:
2
November
2000
Revised:
1
March
2002
Published online:
28
June
2002
The expansion structure of a CI vector as combination of excitations from a model-space reference determinant is investigated. It is shown that between the linear and the exponential expansions there is a relation which is similar to the single-reference case, if the internal excitations are adsorbed into the reference vector. Moreover, expansions with respect to different determinants are related by a set of linear equations. By using these two properties, a State-Specific Coupled-Cluster formalism is proposed.
PACS: 31.25.-v – Electron correlation calculations for atoms and molecules / 31.15.Dv – Coupled-cluster theory
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002
