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Manuscript Title: Errors in the three CPC versions of the program to calculate the single centre expansion of the electron diatomic-molecule static potential.
Authors: L. Malegat, M. Le Dourneuf, V.K. Lan
Program title: STOEX
Catalogue identifier: AALA_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 41(1986)181
Programming language: Fortran.
Computer: NAS 9080 (IBM COMPATIBLE).
Operating system: VMS/JES3.
RAM: 15 K words
Word size: 32
Keywords: Quantum chemistry, Molecule, Electron, Scattering, Single centre expansion.
Classification: 16.5.

Other versions:
Cat Id Title Reference
ACQW_v1_0 STATIC INTERACTION POTENTIAL CPC 2(1971)261
ACQW_v2_0 OCEP W.F. AND STATIC POTENTIAL CPC 11(1976)237
ACQW_v3_0 ONE CENTRE STATIC POTENTIAL CPC 20(1980)267

Nature of problem:
The accuracy of the cross-sections obtained in the single centre formulation of the electron-molecule scattering problem depends heavily on the quality of the one-centre expansion of the multicentre LCAO molecular orbitals. Therefore, it is desirable to study carefully the convergence of the Slater-type atomic orbitals about a displaced origin.

Solution method:
The molecular wavefunction is obtained from an LCAO-MO-SCF calculation, using a basis of Slater-type atomic orbitals centered on the two nuclei. These Slater orbitals are reexpanded in Lengendre polynomials about a unique centre. Single centre expansions of the molecular orbitals and static interaction then follow.

Restrictions:
The original program had limitations concerning the possible n,l values of the Slater orbitals to be expanded, the number of terms in the expansions... These limits were difficult to overcome. The present adaptation makes extensions easy, owing to the use of parametrized dimensions.

Running time:
15s on NAS 9080 for 300 mesh points, 24 atomic orbitals, 1 molecular orbital, 21 terms in the expansions of the atomic and molecular orbitals, 25 terms in the expansion of the static potential.