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Manuscript Title: A compact program of the SCF-Xalpha scattered wave method.
Authors: S. Katsuki, P. Palting, S. Huzinaga
Program title: MSXALPHA
Catalogue identifier: ACXN_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 14(1978)13
Programming language: Fortran.
Computer: AMDAHL 470V/6.
Operating system: MTS.
RAM: 438K words
Word size: 8
Peripherals: magnetic tape, disc.
Keywords: Quantum chemistry, Molecular physics, Structure, Orbital, Energy level, Muffin-tin approximation, Non-overlapping sphere, Xalpha approximation, Initial atomic orbital, Ground state, Transition state.
Classification: 16.1.

Revision history:
Type Tit le Reference
correction 000ACORRECTION 07/09/79 See below

Nature of problem:
The present program calculates molecular orbitals and energy levels by solving the MSXalpha equations in the muffin-tin approximation for the case of non-overlapping contingent spheres. These calculations are done for the ground-state configuration and transition-state theory is used to compute electronic transitions.

Solution method:
Initial atomic orbitals are used to generate the potential in the Xalpha approximation with appropriate division of the molecular space into spherical regions. Radial Schrodinger equations are solved by the Runge-Kutta-Milne method in the spherical atomic regions and the extra molecular region. Energy eigenvalues and eignevectors for the interatomic region are obtained from determining the zeros of the secular determinant with the aid of the Gaussian elimination method with complete pivoting. Special procedures are used to distinguish zeros from poles and to speed up the calculation of these zeros in subsequent iterations. With the newly found molecular orbitals the procedure of determining the potential, eigenvalues, and molecular orbitals is repeated until the eigenvalues convergence.

Restrictions:
The present version of the program handles only the spin restricted case.

Unusual features:
The present version of the program permits one to use analytic Hartree- Fock orbitals in an STO or GTO basis or numerical orbitals as the inital atomic orbitals. Provision is made to do a calculation piece-wise and to make restarts from a given iteration. Core orbitals may be frozen during a calculation. Once valence levels are well behaved, they are automatically treated as core-like orbitals; this provision speeds up the search for zeros of the secular determinant and here reduces the time consumed for each iteration. FORTRAN compatibility The present program is written in IBM FORTRAN IV. The following features used in the program may not be compatible with other FORTRAN languages:
(1) arrays COEFF and DZT are four-dimensional;
(2) apostrophes are used in Format statements to define hollerith strings instead of the standard field description nH;
(3) array element expressions which involve more than one variable or another array element are used, e.g. SYMOVL (I2+IW, ), NDG(IRG3(I));
(4) IMPLICIT REAL*8 and COMPLEX*16 are used;
(5) characters, e and #, are used in column 6 for continuation lines which may possibly cause problems on other computers, and
(6) the ENTRY statement is used.

Running time:
The CPU time required for the calculation mentioned in the test run was about 3 min on the Amdahl 470V/6.

CORRECTION SUMMARY
Manuscript Title: A compact program of the SCF-Xalpha scattered wave method. (C.P.C. 14(1978)13).
Authors: S. Katsuki, P. Palting, S. Huzinaga
Program title: 000ACORRECTION 07/09/79
Catalogue identifier: ACXN_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 18(1979)441
Classification: 16.1.