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Manuscript Title: A general program for computing angular integrals of the Breit-Pauli hamiltonian.
Authors: A. Hibbert, R. Glass, C.F. Fischer
Program title: MCHF_BREIT
Catalogue identifier: ABZY_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 64(1991)455
Programming language: Fortran.
Computer: VAX 11/780.
Operating system: VMS, SUN UNIX.
RAM: 210K words
Word size: 32
Peripherals: disc.
Keywords: Atomic physics, Structure, Configuration, Interaction, Relativistic shift, Spin-orbit interaction, Fine structure splitting, Complex atoms, Functions wave, Bound states, Lsj coupling.
Classification: 2.1.

Subprograms used:
Cat Id Title Reference
ABZU_v1_0 MCHF_LIBRARIES CPC 64(1991)399

Nature of problem:
In the Breit-Pauli LSJ approximation, the wave function is expanded in terms of configuration state functions with differing LS term values. To determine the coefficients in the expansion, the interaction matrix elements need to be expressed in terms of sums of radial integrals. This program calculates the coefficients of these integrals and produces a file INT.LST appropriate for input to the MCHF_CI program.

Solution method:
The coefficients of the integrals are obtained from integration over all spin and angular coordinates. Integration over the radial coordinates is expressed either as unity, zero, or as expressions for radial integrals. A scheme for calculating the coefficients for non- relativistic operators was described by Fano [1], which formed the basis of the earlier WEIGHTS program [2] for orthonormal orbitals. The method for calculating the coefficients for Breit-Pauli operators was described by Glass and Hibbert [3].

Restrictions:
Any number of s-, p-, or d- electrons are allowed in a shell, but no more than two electrons in a shell with l>=3. If l>=4, the LS term for the shell is restricted to those allowed for l=4. Only the shells outside a set of closed shells common to all configurations need be specified. A maximum of 5 (five) shells (in addition to common closed shells) is allowed. This restriction may be removed by changing dimension statements and some format statements.

Running time:
The time required for the first test run is 1.5 seconds and 336.3 seconds for the second test run on a SUN 3/160 with a floating point board.

References:
[1] U. Fano, Phys. Rev. 140(1965)A67.
[2] A. Hibbert, Computer Phys. Commun. (1970)359; 2(1971)180; 6(1973)59.
[3] R. Glass and A. Hibbert, Computer Phys. Commun. 16(1978)19.