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Manuscript Title: Local mode vibrations in tetrahedral molecules.
Authors: L. Halonen, M.S. Child
Program title: TETRA
Catalogue identifier: ABDS_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 51(1988)173
Programming language: Fortran.
Computer: AS/8043.
Operating system: IBM VM/SP.
RAM: 217K words
Word size: 32
Peripherals: disc.
Keywords: Molecular, Vibrations.
Classification: 16.3.

Nature of problem:
The purpose is to investigate the stretching vibrational energy level structure of XY4 tetrahedral molecules with a curvilinear internal coordinate Hamiltonian. The bending degrees of freedom are constrained to the equilibrium values.

Solution method:
The vibrational eigenvalues are obtained variationally using symmetrised Morse oscillator eigenfunctions as basis. Potential energy parameters can be optimised by the non-linear least squares method with experiment- ally observed energy levels as data.

The maximum total stretching quantum number vtot is 12.

Unusual features:
There are three machine dependent constant defined in the hexadecimal form for the IBM 360/370 series in the main program.

Running time:
Running times are of an order of a few minutes in the AS/8043 computer when a least squares calculation is performed with vtot = 9 for one isotopic species.