Partial retention of diatomic differential

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. 

Two philosophies have emerged in connection with the various semi-empirical methods (for a review, see Klopman and Evans, 1976). In both cases certain matrix elements are assumed to be negligible, others are computed, and others are chosen according to some criteria. According to one philosophy, the chosen parameters should lead to agreement with exact Hartree-Fock theory. Then, if desired, correlation can be added in some form. Methods called CNDO and INDO are examples of this. A more recent development is the partial retention of diatomic differential overlap (PRDDO) method (see Estreicher et al., 1989). 

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 ... 

PDDO PRDDO RHF SAMO SCF SOGI STO STO-nG UA UHF VB VIP Projectors of Diatomic Differential Overlap Partial Retention of Diatomic Differential Overlap Restricted Hartree-Fock Simulated ab initio Method Self Consistent Field Spin Optimized GVB method Slater Type Orbital Slater Type Orbital expanded in terms of nGTO United Atom Unrestricted Hartree-Fock Valence Bond Vertical Ionization Potential... 

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). 

There have been two approaehes for parametrization of semiempirieal methods. One approach aims at reproducing ab initio MO calculations with the same minimal basis set. This approach is taken in the method of partial retention of diatomic differential overlap (PRDDO). " " The second approach aims at reproducing experimental data and/or high-level ab initio or density functional theory (DFT) calculations. Severe limitations of low-level ab initio ealeulations are well known now, especially for TM species. " As a result, parametrizations of modern semiempirical SCF MO methods follow the seeond approaeh. 

In subsequent work shortly after this original report, Lipscomb and co-workers performed partial retention of diatomic differential overlap (PRDDO) calculations on these supraicosahedral boranes. This work identified three examples of supraicosahedral boranes, namely, BieHie, BigHig, and B22Fl22, where the dianions (i.e., z = 2) were found to undergo Jahn—Teller distortions. The full molecular symmetries were obtained by considering the structure to be a neutral one with only 2n skeletal electrons. 

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... 

The method of partial retention of diatomic differential overlap (PRDDO) was first developed by Halgren and Lipscomb for the elements hydrogen to fluorine, and extended by Marynick and Lipscomb through the first transition series. PRDDO shares characteristics of both ab initio and semi-empirical methods. As in an ab initio approach, PRDDO calculates many two-electron integrals accurately. Like most semiempirical methods, PRDDO employs a minimal basis set (MBS) of Slater orbitals, and uses parameters to increase the accuracy of the method. 

T. A. Halgren and W. N. Lipscomb, Self-consistent-field wave-functions for complex molecules. The approximation of partial retention of diatomic differential overlap, J. Chem. Phys. 58 1569 (1973). 

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