CONFIGURATION INTERACTION WAVE FUNCTIONS BASED ON THE SENIORITY NUMBER

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

Galpagos

Congreso; CONGRESO DE QUÍMICOS TEÓRICOS DE EXPRESIÓN LATINA; 2014

Universidad de San Francisco - Quito

This work studies the configuration interaction (CI) method when an N-electron Hamiltonian is proyected on Slater determinants selected according to their seniority number value (gamma)1,2. The formulation of the seniority number and the N-electron spin-squared operators in terms of spin-free replacement operators allows us to analyze the spin features of the wave functions provided by that procedure, showing that they have no spin contamination3. The computational cost is evaluated in terms of the size of the matrices required to implement this treatement in any system, for any spin symmetry. The performance of these seniority-number-based CI expansions in several molecular orbital bases is also investigated. Our results indicate that the basis set in which the seniority number operator expectation value is minimun (Mmin) leads to energy values closer to those provided by the FCI level. (1) L. Bytautas, T. M. Henderson, C. A. Jimenez-Hoyos, J. K. Ellis, and G. S. 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, 124114 (2014).