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Manuscript Title: ALAM: a program for the calculation and expansion of molecular charge densities.
Authors: M.A. Morrison
Program title: ALAM
Catalogue identifier: ACZW_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 21(1980)63
Programming language: Fortran.
Computer: CDC 6000-7000 SERIES.
Operating system: KRONOS 2.1.
RAM: 65K words
Word size: 60
Peripherals: disc.
Keywords: Quantum chemistry, Molecule, Charge density, Single centre expansion, Scattering, Electron.
Classification: 16.5.

Nature of problem:
The single-electron probability density function for a closed-shell linear diatomic or triatomic molecule is calculated from a single- configuration molecular-orbital wavefunction that is made up of nucleus-centred Slater-Type-Orbitals (STO's). The resulting function is expanded in Legendre polynomials in a single-centre coordinate system.

Solution method:
The nucleus-centred basis functions are transformed to single-centre coordinates, taking into account different conventions used in the definition of the nuclear geometry, spherical harmonics and molecular orbitals. The expansion in Legendre polynomials is carried out by Gauss Legendre quadrature. Several user options are incorporated so as to avoid repetitive calculation of the charge density.

No more than three nuclear centres can be accomodated. Only linear molecules (belonging to the point groups D infinity h or C infinity v) are allowed. Other parameters, such as array lengths, can be adjusted by the user.

Running time:
For the ground state of LiH, calculation of the charge density requires 0.38 s of CPU time. Each value of a lambda(r) requires 0.01 s.