On the exact (whole) diagonalization of large semi-empirical configuration interaction matrices

Abstract

We propose here a computational approach that is very efficient in performing the whole diagonalization of a configuration interaction (CI) matrix. The efficiency of the approach has been established by calculating all the eigenvectors of a semi-empirical full CI matrix representing the pi structure of the 1,2-benzopentacene. This CI matrix, with a dimension of the order of a million, was diagonalized in a few hours with a standard PC.

On the theoretical analysis of the lowest many-electron states for cyclic zigzag graphene nano-ribbons

“…We have performed massive computational CI calculations for several, of different size, cyclic PAHs. The calculations were performed to topological (parameter-free) whole (all the states) full (all the determinants) CI (many-body) level [26]. A full CI space is invariant under any MO rotation.…”

“…In order to obtain a proper description of the electronic states it is necessary to use a many-determinant representation of their wave functions, what is equivalent to perform a restricted configuration interaction (CI) calculation [26,27]. Plasser et al [8] and Dutta et al [14] have presented CI results for the ground state.…”