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Manuscript Title: II. A program for computing normal modes of molecules, crystal phonon dispersion relations and structure factors for neutron inelastic scattering.
Authors: F.Y. Hansen
Program title: FYFRE
Catalogue identifier: ACXR_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 14(1978)219
Programming language: Fortran.
Computer: IBM 370/165.
Operating system: OS/MVT RELEASE 21.7.
RAM: 575K words
Word size: 32
Peripherals: disc.
Keywords: Solid state physics, Crystal structure, Scattering, Normal mode, Neutron, Factor structure, Dispersion relation, Group theory, Dynamical matrix, Molecule, Phonon, Annihilation, Creation.
Classification: 7.6, 7.8.

Subprograms used:
Cat Id Title Reference
ACXQ_v1_0 FYCOOR CPC 14(1978)193
ACXS_v1_0 FYADJ CPC 14(1978)245

Revision history:
Type Tit le Reference
correction 000A CORRECTION 22/12/78 See below

Nature of problem:
The calculation of normal modes in molecules and crystals based on a harmonic potential field defined in terms of any set of coordinates. For crystals the structure factors and partial differential cross- sections for inelastic one phonon annihilation processes and one phonon creation processes are calculated taking temperature effects into account. Also, the polarization factors for each atom in the unit cell is calculated for each normal mode.

Solution method:
The calculations are based on the results of program FYCOOR described in part I, which generates a complete set of coordinates and force matrices from a very limited input of basis coordinates. These results are stored on permanent units and used in the present program, which calculates the dynamical matrix by simple matrix operations. Symmetry coordinate matrices are used to block diagonalize the dynamical matrix. Once the normal frequencies and eigenvectors have been calculated the inelastic one phonon structure factors and related quantities are calculated.

Unusual features:
The storage requirement depends on the problem that is the number of atoms in the unit cell or in the molecule, the number of basis coordinates and the number of updated force constants. In the present set up the storage requirement is set to 57500 words, which is estimated to be sufficient for a number of cases. Up to 20 basis coordinates, 10 atoms per unit cell or per molecule and 30 updates of force constants may be considered. For a more precise estimate of the storage requirement one should consult the long write-up. Detailed information on how to change storage requirements may also be found there.

Running time:
The running time depends on the problem. For the two test runs the running times including the compilation time were 16 s and 18 s. The compilation time is 12 s.

CORRECTION SUMMARY
Manuscript Title: II. A program for computing normal modes of molecules, crystal phonon dispersion relations and structure factors for neutron inelastic scattering. (C.P.C. 14(1978)219).
Authors: F.Y. Hansen
Program title: 000A CORRECTION 22/12/78
Catalogue identifier: ACXR_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 17(1979)423
Classification: 7.6, 7.8.