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Abstract
The problems of using numerically defined atomic orbital basis functions in MO-LCAO calculations are studied. Such functions may be practical alternatives to contracted Gaussian orbitals. Methods for expanding angular momentum wave functions defined on one centre in terms of angular momentum wave functions on another centre as well as the problem of expanding the product of two such functions about a third centre are reviewed. The application of these methods to the calculation of the required multicentre integrals is described and estimates of the numerical accuracy of the methods are given. The variational equations corresponding to the Hartree–Fock equations are developed, and the methods for their solution discussed. Examples of the application of the methods to two small molecules are given.
Acknowledgements
I have been motivated in this work by frequent visits to the Quantum Theory Project at the University of Florida, and discussions with its members, particularly R.J. Bartlett, H.J. Monkhorst, and So Hirata and by the stimulating atmosphere at many Sanibel meetings. This research is supported by the Natural Sciences and Engineering Reseach Council of Canada. The calculations have been made using the facilities of the Shared Heirarchical Academic Research Computing Network (SHARCNET).