PROGRAM SUMMARY
Title of program:
LILIX
Catalogue identifier:
ADQF
Ref. in CPC:
147(2002)834
Distribution format: gzip file
Operating system: MS-DOS, Unix
Number of lines in distributed program, including test data, etc:
1851
Keywords:
Coupled channel Schrodinger equation, Initial value problem,
CP methods, Variable steps, Regularization, General purpose,
Differential equations.
Programming language used: Fortran
Computer:
Pentium-based PCs ,
HP Series 9000-715/50-UX.
Nature of physical problem:
Quantum mechanics problems which involve the solution of the coupled
channel Schrodinger equation.
Method of solution:
On each step the solution is advanced by a transfer matrix whose
components are constructed via the CP implementation of the perturbation
series in the diagonalization basis of the local reference potential
matrix. Two orders of perturbation are included, plus some extra
diagonal corrections. The algorithm allows propagating also the
solution of the first derivative of the equation with respect to the
momentum k. The order of the method is six and, for one and the same
partition, the accuracy is practically energy independent.
Typical running time:
The running time/step tau by subroutine LIX depends on the processor and
on the number of equations n. On a laptop with a Pentium II processor
one has tau = 1.9 ms and tau = 9.3 ms for n = 10 and n = 20,
respectively. For bigger n, tau increases as n**3. When the solution
is advanced for both systems of equations (that is the coupled channel
equation and its derivative with respect to k), these times are almost
doubled.