Evaluation of Hylleraas-CI atomic integrals by integration over the coordinates of one electron. II. Four-electron integrals |
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Authors: | María Belén Ruiz |
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Institution: | (1) Instituto de F?sica, Universidad Nacional Aut?noma de M?xico, Apdo. Postal 20-364, 01000 Mexico, Mexico |
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Abstract: | An alternative procedure to the classical method for evaluating the four-electron Hylleraas-CI integrals is given. The method
consists of direct integration over the r
12 coordinate and integration over the coordinates of one of the electrons, reducing the integrals to lower order. The method
based on the earlier work of Calais and L?wdin and of Perkins is extended to the general angular case. In this way it is possible
to solve all of the four-electron integrals appearing in the Hylleraas-CI method. The four-electron integrals are expanded
in three-electron ones which are in turn expanded in two-electron integrals. Finally the two-electron integrals are expanded
into two-electron auxiliary integrals which usually have one negative power. The use of three- and four-electron electron
auxiliary integrals is avoided. Some special cases lead to one- and two-electron auxiliary integrals with negative powers
which do not converge individually but do converge in combination with others. These relations and their solutions are presented,
together with results of various kinds of integrals. |
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Keywords: | |
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