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Manuscript Title: A general program to calculate atomic continuum processes using the R- matrix method.
Authors: K.A. Berrington, P.G. Burke, J.J. Chang, A.T. Chivers, W.D. Robb, K.T. Taylor
Program title: RMATRX STG1
Catalogue identifier: AAHA_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 8(1974)149
Programming language: Fortran.
Computer: ICL 1906A.
Operating system: GEORGE 4.
RAM: 118K words
Word size: 24
Peripherals: disc.
Keywords: Atomic physics, Electron-atom scattering, Electron-ion scattering, Photoionization, Polarizability, R-matrix, Continuum, Bound, Pseudo potential, De vogelaere's method, Radial integrals, Rk integrals, Scattering, Photon.
Classification: 2.4, 2.5.

Subprograms used:
Cat Id Title Reference
AAHB_v1_0 RMATRX STG2 CPC 8(1974)150
AAHC_v1_0 RMATRX STG3 CPC 8(1974)150
AAHE_v1_0 A NEW VERSION OF BASFUN CPC 8(1974)152
ACQB_v1_0 P SHELL C.F.P. CPC 1(1969)15
ACQC_v2_0 A NEW D SHELL CFP CPC 6(1973)88
ACQL_v2_0 WEIGHTS NEW VERSION CPC 2(1971)180
ACQL_v2_0 0001 ADAPT WEIGHTS FOR ONE PART CPC 7(1974)318
AAGD_v2_0 A NEW VERSION OF NJSYM CPC 8(1974)151
AAKF_v1_0 REDUCED TENSOR MATRIX ELEMENTS CPC 6(1973)132
ACRK_v1_0 ASYM VERSION FOR ICL 1900 CPC 5(1973)416

Other versions:
Cat Id Title Reference
AAHF_v1_0 A NEW VERSION OF RMATRX STG1 CPC 14(1978)367
AANR_v1_0 RMATRX STG1R CPC 25(1982)347

Nature of problem:
This program calculates all one-electron, two electron and multipole radial integrals involving the bound and continuum orbitals necessary to enable electron atom or ion scattering, photoionization or frequency dependent polarizabilities to be calculated for a general atomic system. The bound orbitals are specified analytically. The continuum orbitals are calculated by the program. The integrals are stored on a permanent tape or disc file for use by RMATRX STG2.

Solution method:
The continuum orbitals are determined by integrating numerically a differential equation with a given potential using de Volgelaere's method and subject to R-matrix boundary conditions. The one-electron integrals and the multipole integrals are evaluated numerically using Simpson's rule. The RK integrals are determined by solving a different- ial equation and then using Simpson's rule.

Restrictions:
Up to 5 bound orbitals and 20 continuum orbitals for each angular momentum can be included. More orbitals can be included by recompling with larger dimensions. Certain arrays which contain the radial integrals may have to have their dimensions increased for large runs.

Running time:
The running time depends approximately on the square of the number of bound orbitals, on the square of the number of continuum orbitals for each angular momentum and on the number of continuum angular momenta. The test run took 500 s on the ICL 1906A which is equivalent to about 50 s on the IBM 370/195.