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Manuscript Title: FRODO: a MuPAD program to calculate matrix elements between contracted wavefunctions
Authors: C. Angeli, R. Cimiraglia
Program title: FRODO
Catalogue identifier: ADVY_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 171(2005)63
Programming language: MuPAD vs. 2.5.3 for Linux.
Computer: Any computer on which the MuPAD computer algebra system can be installed.
Operating system: Linux.
Keywords: CAS-SCF wavefunctions, internally contracted functions, matrix elements, symbolic algebra.
PACS: 03.67.Lx, 31.15.Ar, 31.25.-v.
Classification: 5.

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.

Solution method:
The method adopted consists in successively eliminating all occurrences of inactive orbital indices (core and virtual) from the products of excitation operators which appear in the definition of the ICF's and in the electronic Hamiltonian expressed in the second quantization formalism.

The program is limited to no more than doubly excited ICF's.