Programs in Physics & Physical Chemistry
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|Manuscript Title: A program for ion-atom collisions involving one electron.|
|Authors: H.G. Morrison, U. Opik|
|Program title: PHCOLL|
|Catalogue identifier: ACPG_v1_0|
Distribution format: gz
|Journal reference: Comput. Phys. Commun. 77(1993)403|
|Programming language: Fortran.|
|Computer: DIGITAL VAX 9210.|
|Operating system: VMS.|
|Keywords: Molecular physics, Ion-atom collisions, Heavy-particle collision, Charge transfer, Electron capture, Excitation collisional, Impact parameter, Transition amplitude, Time-dependent Schrodinger equation, Variational method, Coupled differential Equations, Runge-kutta method, Orthogonal polynomials, Gaussian-type quadrature.|
Nature of problem:
Computation of transition amplitudes for ion-atom collisions in the impact-parameter formulation .
The time-dependent wave function is expanded in orthogonal polynomials in coordinates that are linear functions of the distances of the electron from the two nuclei. A variational method is used for large internuclear distances, and coupled differential equations are integrated step by step for smaller internuclear distances .
The total physical system may consist of only two nuclei and one electron. However, it should be fairly easy to adapt the program so that it will handle a system consisting of two ionic cores and one active electron.
Most large arrays are defined in three so-called sub-master programs (subroutines) as non-common arrays, so that the user can easily change their dimensions by altering a few PARAMETER statements. The naming of variables and arrays follows the recommendations of Roberts .
Propagation of a wave function from time t=-infinity to a value t=t1 from which the computation could be continued by step-by-step integration, in a typical test, took 5.6 seconds. Step-by-step integration with 112 basis functions took 0.30 seconds per step; between 100 and 160 steps are usually needed. With 365 basis functions, step-by -step integration took 3.0 seconds per step. In the latter computation the step length was one-half of that in the former, so the effective increase in time expenditure was by a factor of 20. 112 basis functions seemed to give sufficient accuracy. Computation of a transition amplitude takes of the order of 10 seconds if the time integral terms in eq. (5.1) of the Long Write-up are present, and a negligible amount of time without these.
|||A. Balfour and D.H. Marwick, Programming in Standard FORTRAN 77 (Heinemann, London, 1979).|
|||H.G Morrison and U. Opik, J. Phys. B 11 (1978) 473.|
|||K.V. Roberts, Comput. Phys. Commun. 1 (1969) 1.|
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