# FRODO: a MuPAD program to calculate matrix elements between contracted wavefunctions

## Description

Abstract A symbolic program performing the Formal Reduction of Density Operators (FRODO) has been developed in the MuPAD computer algebra system with the purpose of evaluating the matrix elements of the electronic Hamiltonian between internally contracted functions in a complete active space (CAS) scheme. The program is illustrated making use of two meaningful examples. Title of program: FRODO Catalogue Id: ADVY_v1_0 Nature of problem In order to improve on the CAS-SCF wavefunction one can resort to multireference perturbation theory or configuration interaction based on internally contracted functions (ICF) which are obtained by application of the excitation operators to the reference CAS-SCF wavefunction. The formulation of such matrix elements is quite cumbersome and a computer algebra system like MuPAD appears ideally suited to perform such a task. Versions of this program held in the CPC repository in Mendeley Data ADVY_v1_0; FRODO; 10.1016/j.cpc.2005.05.002 ADVY_v2_0; FRODO; 10.1016/j.cpc.2012.09.034 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018)