Elsevier Science Home
Computer Physics Communications Program Library
Full text online from Science Direct
Programs in Physics & Physical Chemistry
CPC Home

[Licence| Download | New Version Template] aahc_v1_0.gz(44 Kbytes)
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 STG3
Catalogue identifier: AAHC_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 8(1974)149
Programming language: Fortran.
Computer: ICL 1906A.
Operating system: GEORGE 4.
RAM: 78K words
Word size: 24
Peripherals: disc.
Keywords: Atomic physics, Electron-atom scattering, Electron-ion scattering, Polarizability, R-matrix, Hamiltonian matrix, Householder method, Eigenvalues, Eigenvectors, Cross-sections, Buttle correction, De vogelaere's method, Phase shifts, K-matrix, Long range potentials, Asymptotic solutions, Wbk, Scattering, Photon.
Classification: 2.4, 2.5.

Subprograms used:
Cat Id Title Reference
AAHE_v1_0 A NEW VERSION OF BASFUN CPC 8(1974)152
ACRK_v1_0 ASYM VERSION FOR ICL 1900 CPC 5(1973)416
AAHA_v1_0 RMATRX STG1 CPC 8(1974)149
AAHB_v1_0 RMATRX STG2 CPC 8(1974)150
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

Other versions:
Cat Id Title Reference
AAHH_v1_0 A NEW VERSION OF RMATRX STG3 CPC 14(1978)367
AANV_v1_0 RMATRX STG3R CPC 25(1982)347

Nature of problem:
This program reads the hamiltonian matrix elements etc. stored on a permanent tape or disc file by RMATRX STG2. It then diagonalizes this matrix and calculates the R-matrix and the Buttle correction. Then either the electron atom or ion cross-section, the photoionization cross-section or the frequency dependent polarizability for a range of incident energies or frequencies is calculated.

Solution method:
The Housholder method and the bisection method are used to diagonalize the hamiltonian matrix and the Buttle correction is caluclated by solving a differential equation using de Volgelaere's method. In the case of electron scattering and photoionization the coupled differential equations are solved in the asymptotic region using either an asymptotic series expansion of a WBK solution. The K-matrix and T-matrix are determined from the R-matrix by matrix algebra.

Restrictions:
The maximum size of the hamiltonian matrix that can be treated is 120, the maximum number of channels is 6 and the maximum number of energies which can be dealt with in one run is 50. All of these can be increased by recompiling.

Running time:
For hamiltonian matrices of order or greater than about 100 the time is dominated by the diagonalization procedure. For smaller matrices the time taken to solve the electron scattering equations in the asymptotic region is usually the domainating factor if more than a few energy points are required. The test runs took 55 s for electron scattering, 54 s for photoionization and 10 s for polarizability on the ICL 1906A.