Starting SCF calculations by superposition of atomic densities.
We describe the procedure to start an SCF calculation of the general type from a sum of atomic electron densities, as implemented in GAMESS-UK. Although the procedure is well known for closed-shell calculations and was already suggested when the Direct SCF procedure was proposed, the general procedure is less obvious. For instance, there is no need to converge the corresponding closed-shell Hartree-Fock calculation when dealing with an open-shell species. We describe the various choices and illustrate them with test calculations, showing that the procedure is easier, and on average better, than starting from a converged minimal basis calculation and much better than using a bare nucleus Hamiltonian.
Theoretical Chemistry Group, Department of Organic Chemistry and Catalysis, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. joop@chem.uu.nl
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Van Lenthe
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Van Dam
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