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Manuscript Title: DVR3D: programs for fully pointwise calculation of vibrational spectra.
Authors: J.R. Henderson, C.R. Le Sueur, J. Tennyson
Program title: DVR3D
Catalogue identifier: ACNE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 75(1993)379
Programming language: Fortran.
Computer: Convex C3840.
Operating system: BSD UNIX.
Word size: 32
Peripherals: disc.
Keywords: Molecular physics, Vibrations, Body-fixed, Discrete variable Representation, Coriolis decoupled, Finite elements, Gaussian quadrature, Vectorised.
Classification: 16.3.

Nature of problem:
DVR3D calculates the bound vibrational or Coriolis decoupled ro- vibrational states of a triatomic system in body-fixed Jacobi (scattering) or Radau coordinates coordinates [1].

Solution method:
All co-ordinates are treated in a discrete variable representation (DVR). The angular coordinate uses a DVR based on (associated) Legendre polynomials and the radial coordinates utilise a DVR based on either Morse oscillator-like or spherical oscillator functions. Intermediate diagonalisation and truncation is performed on the hierarchical expression of the Hamiltonian operator to yield the final secular problem. DVR3D provides the data necessary for DIPJ0DVR [2] to calculate vibrational band intensities.

(1) The size of the final Hamiltonian matrix that can practically be diagonalised. DVR3D allocates arrays dynamically at execution time and in the present version the total space available is a single parameter which can be reset as required. (2) The order of integration in the radial co-ordinates that can e dealt within the machine exponent range. Some adjustment in the code may be necessary when large order Gauss-Laguerre quadrature is used.

Unusual features:
A user supplied subroutine containing the potential energy as an analytic function (optionally a Legendre polynomial expansion) is a program requirement.

Running time:
Case dependent but dominated by the final (3D) matrix diagonalisation. The test data takes 229 sec on a Convex C3840.

[1] J.R. Henderson, PhD Thesis, University of London (1990)
[2] J.R. Henderson, C.R. Le Sueur and J. Tennyson, this article, second program (DIPJ0DVR).