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Manuscript Title: Pseudopotential matrix elements in the Gaussian basis.
Authors: M. Kolar
Program title: PSEPO1
Catalogue identifier: AAQM_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 23(1981)275
Programming language: Fortran.
Computer: IBM 370/135.
Operating system: OS/VS1.
RAM: 9K words
Word size: 32
Peripherals: disc.
Keywords: Structure, Gaussian, Expansion, Direct-access device, Pseudopotential, Molecule, Quantum chemistry, Matrix element, Cluster, Lcao, Integral.
Classification: 16.1, 16.10.

Subprograms used:
Cat Id Title Reference
AAQN_v1_0 COMPANGI CPC 23(1981)275

Other versions:
Cat Id Title Reference
AAQL_v1_0 PSEPOT CPC 23(1981)275

Nature of problem:
The incorporation of atomic pseudopotentials in the calculation of the electronic structure of molecules and larger complexes leads to a decrease in the size of the problem since in the frozen core approximation only valence electrons need to be considered. PSEPOT is a subprogram that computes matrix elements of atomic pseudopotentials occuring in the above mentioned calculations provided that both the pseudopotentials and the basis functions are expressed as linear combinations of different Gaussians.

Solution method:
The rather complex expression for the pseduopotential matrix elements can be decomposed into a linear combination of the products of different more or less elementary integrals. The final result is obtained roughly speaking by performing a sequence of scalar products arranged in such a manner that no more extensive calculation must be repeated twice.

Restrictions:
Largest pseduopotential orbital angular momentum Lmax<= 2. Largest basis-orbital angular momentum nmax= 3.

Unusual features:
A set of 6480 angular integrals were precalculated and placed in a few DATA statements.

Running time:
The running time depends considerably on the values of the angular momenta involved and on the number of Gaussians in the pseudopotential expansion. The average value for the test run was 3.6 s per matrix element.