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[Licence| Download | New Version Template] acqw_v2_0.gz(24 Kbytes)
Manuscript Title: A new version of a program calculating the static interaction potential between an electron and a diatomic molecule.
Authors: F.A. Gianturco
Catalogue identifier: ACQW_v2_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 11(1976)237
Programming language: Fortran.
Computer: ICL 1906A.
Operating system: GEORGE 4.
RAM: 187K words
Word size: 24
Peripherals: magnetic tape.
Keywords: Quantum chemistry, Molecule, Electron, Single-centre expansion, Static potential, Dipole moment, Quadrupole moment, Multipolar expansions, Scattering.
Classification: 16.5.

Nature of problem:
This program calculates in one-centre expansion (OCE) form the wavefunction for a diatomic molecule and also the multipolar expansion of its static interaction with a point charge. It corrects some errors contained in a previous version of this program and provides both potential and wave function in a form suitable for using in a program to calculate electron molecule scattering.

Solution method:
The original two-centre wavefunction is assumed to be given by a single -determinantal (closed-shell) representation from an LCAO-MO-SCF calculation. Each of the occupied molecular orbitals (MO's) is described by an expansion over Slater-type functions (STO's) centred on either of the two nuclei of the molecule. The atomic orbitals are then expanded in Legendre polynomials around the centre of mass and the resulting single particle wavefunctions, once orthonormalized, are used to calculate the static potential.

The maximum number of basis set functions is 50, for a maximum total number of 10 MO's. The once-centre expansion of the wavefunction can be carried out up to 21 terms and the potential multipolar expansion up to 26 terms. These limits can be extended by altering the dimensions of the arrays.

Running time:
To evaluate a set of MO at 1 value of r takes about 0.5 s on an IBM 30/75 machine. Similarly to evaluate a set of static potentials at one radial value r takes about 0.5 s.