PRDDO partial retention of diatomic

The PRDDO (partial retention of diatomic differential overlap) method is an attempt to get the optimal ratio of accuracy to CPU time. It has been parameterized for the periodic elements through Br, including the 3rd row transition metals. It was parameterized to reproduce ah initio results. PRDDO has been used primarily for inorganic compounds, organometallics, solid-state calculations, and polymer modeling. This method has seen less use than other methods of similar accuracy mostly due to the fact that it has not been incorporated into the most widely used semiempirical software. 

Of comparable or better accuracy, but much faster, is the PRDDO (Partial Retention of Diatomic Differential Overlap) method proposed by Halgren and Lipscomb.66 This method uses the exact one-electron matrix over STOs transformed to an orthogonal atomic orbital (OAO) basis.66 Electron-repulsion integrals are systematically approximated using exact values of some integrals over the original STO basis. The method recognizes three basis sets ... 

A promising semi-rigorous molecular orbital method, PRDDO, partial retention of diatomic differential overlap has been reported in the interim [186]. Also, the method of diatomics-in-molecules has been revived and the derivations extended to include p orbitals appropriately [187]. 

Ab initio SCF calculations have yielded wavefunctions for B8H1Z, B9H15, BeHl-, B10H10, and BioH L24 These have been compared with the results of an approximate calculation using the PRDDO (partial retention of diatomic differential overlap) method. The latter was found to give quite satisfactory results, for much less computing time. 

PRDDO (partial retention of diatomic differential overlap) calculations have... 

Numerous ab initio calculations with at least split-valency quality basis sets have been performed. The results are extremely sensitive to the choice of the basis set, especially the inclusion of d orbitals, and to the procedure applied, such as nth-order Moller-Plesset theory (MPn, up to n = 4) [3 to 7], coupled electron pair approximation (CEPA) [1,2, 8, 9], configuration interaction (Cl) [8, 10, 11], or SCF MO calculations [12 to 19]. For semiempirical calculations, see [20, 21 ] (EHMO), [22] (PRDDO, partial retention of diatomic differential overlap), and [23] (INDO, intermediate neglect of differential overlap). 

FCP = frozen core potential MBS = minimum basis set NQOAO = not quite orthogonal atomic orbital OAO = orthogonal atomic orbital PESP = parametrized electrostatic potential PRDDO = partial retention of diatomic differential... 

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