Programs in Physics & Physical Chemistry
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|Manuscript Title: A program to introduce local symmetry in ab initio computations of molecules: IBMOL-7.|
|Authors: E. Ortoleva, G. Castiglione, E. Clementi|
|Program title: IBMOL-7|
|Catalogue identifier: ACYY_v1_0|
Distribution format: gz
|Journal reference: Comput. Phys. Commun. 19(1980)337|
|Programming language: Fortran.|
|Computer: UNIVAC 1100/20.|
|Operating system: EXEC 8.|
|Program overlaid: yes|
|RAM: 64K words|
|Word size: 36|
|Keywords: Symmetry, Local symmetry, Integral, Molecular physics, Ab initio computation, Structure.|
|Classification: 16.1, 16.10.|
Nature of problem:
In ab initio computations on large molecules many two-electron multi- centre integrals can be saved when groups of centres repeat in the molecule. A program is made to automatically detect and exploit such repetitions without using point group symmetry.
All the four-centre groups are virtually compared; a list of equivalent groups, and related geometrical transformations, precedes the evaluation of four-centre two-electron integrals.
The program uses sort subroutines, supplied by the UNIVAC system library the link with sort must be modified when other machines and therefore other sort subroutines are used. UNIVAC FORTRAN V quarter-word handling functions (FLD) are used: they can be translated, rather easily, into single byte instructions for IBM 360 or 370 series machines. Some functions needing information from the operating system require small assembler routines.
Running time is strongly dependent on the dimensions of the molecules: in the Long write-up this dependence is analyzed in detail.
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