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Manuscript Title: Electron scattering by closed or open shell diatomic molecules.
Authors: G. Raseev
Program title: ELECTRON MOLECULE SCATTERING
Catalogue identifier: ACZS_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 20(1980)275
Programming language: Fortran.
Computer: IBM 370/168.
Operating system: JES 3 AND ASP.
RAM: 640K words
Word size: 32
Peripherals: disc.
Keywords: Quantum chemistry, Electron, Open shells, Single centre expansion, Continuum hartree fock, Cross sections, Scattering, Molecule.
Classification: 16.5.

Subprograms used:
Cat Id Title Reference
ACQW_v3_0 ONE CENTRE STATIC POTENTIAL CPC 20(1980)267

Other versions:
Cat Id Title Reference
ACQO_v1_0 ELECTRON MOLECULE SCATTERING CPC 1(1970)445

Nature of problem:
An extension of the existing low-energy electron diatomic molecule scattering program to open-shell molecular targets is presented. In this version, the orthogonalisation between bound and continuum orbitals is introduced. The K matrix elements and the eigen-phases for rotational excitation are evaluated. The final continuum wave function is also calculated and stored on file.

Solution method:
The approach is based on a single-centre expansion of the molecular and incident electron orbitals. This centre can be any point for example the centre of mass, one of the atoms or the centre of charge of the molecule. The target molecule is represented by a LCAO-MO-SCF wave function which can be of closed or restricted open-shell type. It is assumed that the molecular axis does not rotate during the collision. The coupled integro-differential equations, with an orthogonalisation constraint and a modified exchange function (Raseev et al.) are solved by a method analogous to the electron atom case.

Restrictions:
The program written in FORTRAN is dynamically allocated by an interface written in assembler (370/168). This interface can be replaced by a small FORTRAN main program provided with the program.

Running time:
The test run of CH(**2Sigma+(**1Phi + e(phi)) with 200 mesh points which is about a half of the standard value requires about 23 s on an IBM 370/ 168. This test uses a five-term potential, has 6 compact exchange functions and performs the orthogonalisation with a 1phi orbital.