Direct selected configuration interaction using a hole-particle formalism

✍ Scribed by Rosa Caballol; Jean-Paul Malrieu

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 498 KB
• Volume: 188
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(92)80863-7

✦ Synopsis

The outlines of a direct selected configuration interaction algorithm are given. The selected determinants q~l are identified as products of a and fl spins multiple excitations from the reference determinant qb o, in a hole-particle formalism. This formulation is compact and in the action of the c~a (or/3fl) 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 NH 3 for which fulI-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.