Programs in Physics & Physical Chemistry
|[Licence| Download | New Version Template] aaoe_v1_0.gz(41 Kbytes)|
|Manuscript Title: VPM: a new asymptotic package.|
|Authors: J.P. Croskery, N.S. Scott, K.L. Bell, K.A. Berrington|
|Program title: VPM|
|Catalogue identifier: AAOE_v1_0|
Distribution format: gz
|Journal reference: Comput. Phys. Commun. 27(1982)385|
|Programming language: Fortran.|
|Operating system: COS 1.10.|
|RAM: 0K words|
|Word size: 64|
|Keywords: General purpose, Differential equation, Asymptotic solutions, Electron-atom, Electron-molecule, Scattering, Photodetachment, Free-free, Variable phase, R-matrix, Long-range potential.|
Nature of problem:
This program solves the outer region coupled equations which occur in electron-atom, electron-molecule scattering and obtains the scattering K-matrix together with slowing varying amplitudes from which the wavefunctions and their derivatives may readily be obtained.
The equations are solved using a method which is generally based on the variable phase method discussed by Calogero, but modified to take into account the peculiar features of the first order non-linear ordinary differential equations. The differential equations are solved using the powerful and stable package of Shampine and Gordon.
The current version cannot treat the case of (i) a Coulombic potential, (ii) all closed channels. A modified version to treat these cases is in preparation. Restrictions due to dimension sizes may be easily alleviated by altering PARAMETER statements (see listing for details).
The running time depends critically upon: the number of channels included; the number of open channels; the convergence radius for the asymptotic analytic expansions employed; energies near thresholds or in resonance regions; and whether one is performing only a K-matrix calculation or a full K-matrix plus wavefunction calculation. Typically a full calculation takes approximately three times longer than a K- matrix only calculation. The test run took 10.5 s on the CR AY-1. CRAY-1.
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