PROGRAM SUMMARY
Title of program:
FLAC
Catalogue identifier:
ADNF
Ref. in CPC:
133(2000)66
Distribution format: tar gzip file
Operating system: Digital UNIX 4.0E, Windows NT pack 4, MacOS9.0.2
High speed store required:
640K words
Number of bits in a word:
32
Number of lines in distributed program, including test data, etc:
25403
Keywords:
Small-angle scattering, Hard spheres, Polydispersity, Percus-Yevick,
Mean spherical approximation, Solid state physics, Neutron.
Programming language used: Fortran
Computer:
DigitalWorkstation AU433,
Pentium I MMX 200 MHz ,
Macintosh Powerbook G3 .
Nature of problem:
The problem is the calculation of the scattering cross section in
small-angle scattering of polydisperse neutral and charged hard spheres.
Both dense or dilute systems are considered.
Method of solution:
The algorithms implemented here are obtained by solving the
Orstein-Zernike integral equations within the Percus-Yevick and mean
spherical approximation closures for neutral and charged hard spheres,
respectively [1,2].
Restrictions:
Only hard sphere (neutral or charged) potentials are used.
Typical running time:
A test run considers 200 points for defining the size distribution
function and calculates the scattering cross section over 2^13 points,
without any smearing effects. For neutral hard spheres, on a Digital
Workstation AU 433 this test takes 7.7 s, while on the Macintosh and on
the PC 26.1 and 49.6 s, respectively. On including instrumental
smearing considering only one experimental configuration (by convoluting
over 11 points) the CPU time on the Digital Workstation AU 433 increases
up to 46.8 s; if multiple scattering correction is also taken into
account (by using 2^7 points for the 2D Fourier transform), the CPU time
is 47.3 s. Furthermore, the addition of a vertical slit (sampled by
2^6 points) requires 270.1 s of CPU time. For charged hard spheres, the
calculation without any correction takes 12.1 s of CPU time.
Unusual features:
Routines of the Harwell Subroutine Library (HSL) are included. Their
use must be acknowledged in any paper publishing results obtained by
FLAC. The entire code must be linked with the International
Mathematical Statistical Libraries (IMSL).
References:
[1] A. Vrij, J. Chem. Phys. 69 (1978) 1742; 71 (1979) 3267.
[2] D. Gazzillo, A. Giacometti, F. Carsughi, J. Chem. Phys.
107 (1997) 10141.