Configuration Interaction Wave Functions Based On The Seniority Number

A. TORRE; L. LAIN; D.R. ALCOBA; G.E. MASSACCESI; O.B. OÑA

Isla de San Cristobal

Congreso; 40th Congress Of Theoretical Chemists Of Latin Expression - Chitel Xl; 2014

Universidad San Francisco de Quito

This work deals with the N-electron wave functions arising from the configuration interaction method when an N-electron Hamiltonian is projected on Slater determinants classified according to their seniority number [1]. The spin properties (spin contamination) of the wave functions provided by this method are analyzed and compared with those resulting from the traditional configuration interaction procedure, based on Slater determinant classifications according to excitations from a determined reference state. The computational expense required in the seniority-number-based treatment has been calculated in terms of the size of the matrices utilized to formulate the states of any spin symmetry within this framework. In order to know the performance of this configuration interaction method, we have determined correlation energies, at identical level of seniority number in several basis sets. The results show that the basis set in which the expectation value of the seniority number operator is minimum yields energy values closer to those provided by the full configuration level. References: [1] Alcoba, D.R., Torre, A., Lain, L., Massaccesi, G.E., Oña, O.B. J. Chem. Phys. 2013. 139, 084103