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Manuscript Title: Calculation of many-centre two-electron molecular integrals with STO.
Authors: J. Fernandez Rico, R. Lopez, I. Ema, G. Ramirez
Program title: STNGINT
Catalogue identifier: ADGG_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 105(1997)216
Programming language: Fortran.
Computer: IBM RISC 6000.
Operating system: AIX 4.1.
RAM: 108K words
Word size: 32
Keywords: Molecular physics, Slater-type orbitals, Exponential-declining, Orbitals, Molecular, Integrals, Two-electron integrals, Multicenter integrals, Gaussian expansions, Sto-ng expansions.
Classification: 16.10.

Nature of problem:
The program computes the two-electron integrals between four sets of real STOs, placed at differen points, A, B, C and D with exponents zeta A, zeta B, zeta C, zeta D, and quantum numbers NA LA MA, NB LB MB, NC LC MC, ND LD MD for all the combinations of MA, MB, MC, MD that are compatible with a given set of LA, LB, LC, LD.

Solution method:
The integrals are obtained by expanding the STOs in terms of Gaussian functions and using standard techniques. The intermediate results shared by sets of integrals are computed once to save computational time. The integrals are first evaluated in terms of cartesian components and afterwards, in a final step, transformed to the spherical harmonics components.

Restrictions:
Integrals involving STOs with values of the L quantum number from 0 to 3 and with N up to 6 can be computed.

Unusual features:
none

Running time:
For the test deck is 18.61 sec (in an IBM RISC-6000 3CT computer) including input/output time.

References:
[1] R. Lopez and G. Ramirez, J.M. Garcia de la Vega and J. Fernandez Rico. Large Gaussian Expansions of STOs for the Calculation of Many-center Molecular Integrals with Slater Basis. J. Chim. Phys., 84, 695-698 (1987).
[2] J. Fernandez Rico, G. Ramires, R. Lopez and J.I. Fernandez Alonso. Accurate Gaussian Expansion of STOs. Test of Many-center Slater Integrals. Collect. Czech. Chem. Comm., 53, 2250-2265 (1987).
[3] V.R. Saunders. Computational Techniques in Quantum Chemistry and Molecular Physics, G.H.F. Diercksen, B.T. Sutcliffe and A. Veillard, Eds. (D. Reidel, Boston, 1975) 347-392.
[4] J. Fernandez Rico, R. Lopez, I.Ema and G. Ramirez. Computation of Multicenter Molecular Integrals with Large Gaussian Expansions of Slater Type Orbitals. Submitted.