VRDDO approximation

Our VRDDO approximation (variable retention of diatomic differential overlap) was inspired in part by a suggestion from solid state physics by Wilhite and Euwema (1+5) The approximation consists of neglecting all one-electron integrals (both energy and overlap) and two-electron integrals that involve basis function pairs . (1)<(). (1) whose pseudo-overlap ... 

The variable retention of diatomic differential overlap (VRDDO) method of Kaufman and collaborators also uses semiorthogonalization. In addition, VRDDO uses a model potential to eliminate consideration of the inner-shell electrons. Both Kashiwaga s method and the VRDDO method approximate ab initio calculations, and neither introduces empirically based parameters. 

H. E. Popkie and J. J. Kaufman, hit. J. Quantum Chem., Quantum Biolopy Symp., 2, 279 (1975). Test of Charge-Conserving Integral Approximations for a V ariable Retention of Diatomic Differential Overlap (VRDDO) Procedure for Senti-uO Imtio Molecular Orbital Calculations on Large Molecules. 

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