Improved algorithm for the calculation of one‐electron two‐center integrals with STOs

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Abstract
In a previous article (J. Fernández Rico, R. López and G. Ramírez, J. Comp. Chem., 9, 790 (1988)) we have proposed the calculation of molecular integrals involving STOs by means of some recurrence relations which use two sets (h and H) of overlap integrals (basic matrices). In the present paper, we derive explicit expressions of these integrals employing the two‐range expansion of the 0s‐function. This approach yields equations for the elements of the two basic matrices in terms of two further matrices, k(x,y) and i(x,y), and some auxiliary functions. Relations between the elements of these matrices and the functions are thoroughly explored and numerical tests are included for illustrating the behavior of the method.