Compact Configuration Interaction wave functions: hybrid excitation-level and seniority-number approaches

O.B. OÑA; D.R. ALCOBA; A. TORRE; L. LAIN; G.E. MASSACCESI; P. CAPUZZI; M. VAN RAEMDONCK; D. VAN NECK; P. BULTINCK

La Plata

Seminario; Seminario de la División de Química Teórica del Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas del Consejo Nacional de Investigaciones Científicas y Técnicas; 2015

Consejo Nacional de Investigaciones Científicas y Técnicas

The Full Configuration Interaction (FCI) wave functions, usually expressed in terms of N-electron Slater determinants, constitute the exact solutions of the Schrödinger equation of an N-electron system for a given one-electron basis set. However, they render prohibitive computational costs, except for systems having a low number of electrons described by small size basis sets. Consequently, the overcoming of this drawback requires the search of approximated methods. In this presentation we examine different Configuration Interaction (CI) truncation strategies to generate compact wave functions. We focus on the performance of CI methods in which the Hamiltonian of an N-electron system is projected on Slater determinants selected according to the traditional excitation-level procedure and the concept of seniority number of a determinant [1-4]. The compactness and configurational structure of the resulting N-electron wave functions expressed in several types of molecular orbital basis sets are assessed by means of numerical determinations of entropic indices formulated within the Information Theory framework. References: [1] L. Bytautas, T.M. Henderson, C.A. Jiménez-Hoyos, J.K. Ellis, and G.E. Scuseria, J. Chem. Phys 135, 044119 (2011) [2] D.R. Alcoba, A. Torre, L. Lain, G.E. Massaccesi, and O.B. Oña, J. Chem. Phys 139, 084103 (2013) [3] D.R. Alcoba, A. Torre, L. Lain, G.E. Massaccesi, and O.B. Oña, J. Chem. Phys 140, 234103 (2014) [4] D.R. Alcoba, A. Torre, L. Lain, O.B. Oña, P. Capuzzi, M. Van Raemdonck, P. Bultinck, and D. Van Neck, J. Chem. Phys 141, 244118 (2014)