PROGRAM SUMMARY
Title of program:
BIX
Catalogue identifier:
ADRZ
Ref. in CPC:
154(2003)159
Distribution format: tar gzip file
Operating system: Unix, Windows NT 4.0 and XP Professional Ed
High speed store required:
256MK words
Number of lines in distributed program, including test data, etc:
2824
Keywords:
Born approximation, Electron-impact ionisation cross-section, Maple,
Hartree-Fock, Atomic physics, Scattering.
Programming language used: Maple V Release 5.1, Fortran
Computer:
DEC Alpha .
Nature of physical problem:
Calculates the total electron impact ionisation cross-section for
neutral and ionised atomic species using the first-Born approximation.
The scattered electron is modelled by a plane wave, and the ejected
electron is modelled by a hydrogenic Coulomb wave, which is made
orthogonal to all occupied atomic orbitals, and the atomic orbitals are
approximated by Hartree-Fock Slater functions.
Method of solution:
An analytic form of the matrix element is evaluated using the Maple
algebraic computing software. The total ionisation cross-section is
then calculated using a three-dimensional Clenshaw-Curtis numerical
integration algorithm.
Restrictions:
There is no theoretical limit on the quantum state of the target orbital
that can be solved with this methodolgy, subject to the availability of
Hartree-Fock coefficients. However, computing resource limitations will
place a practical limit to, approximately, n<=7 and l<=4. The precision
of results close to the ionisation threshold of larger atoms (<1eV for
Z>48) is limited to ~5%.
Typical running time:
5 to 40 minutes for initial calculation for an atomic orbital, then 5 to
300 seconds for subsequent energies of the same orbital.
Unusual features:
To reduce calculation time, FORTRAN source code is generated and
compiled automatically by the Maple procedures, based upon the analytic
form of the matrix element. Numerical evaluation is then passed to the
FORTRAN executable and the results are retrieved automatically.