Direct selected configuration interaction using a hole-particle formalism
1992; Elsevier BV; Volume: 188; Issue: 5-6 Linguagem: Inglês
10.1016/0009-2614(92)80863-7
ISSN1873-4448
AutoresRosa Caballol, Jean‐Paul Malrieu,
Tópico(s)Spectroscopy and Quantum Chemical Studies
ResumoThe outlines of a direct selected configuration interaction algorithm are given. The selected determinants φI are identified as products of α and β spins multiple excitations from the reference determinant φ0, in a hole-particle formalism. This formulation is compact and in the action of the αα (or ββ) part of H on the current vector avoids consideration of the excitation processes, saving significant computation time. A few examples illustrate the performance of the method, taken from NH3 for which full-CI is known, or a more realistic problem, NiCO2, involving a large number of active MOs (61) and electrons (26). The possible uses of the algorithm in approximate CI methods like CIPSI are discussed.
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