Pople

Pople J 1954 Statistical mechanics of assemblies of axially symmetric molecules I. General theory Proc. R. Soc. A 221 498... 

As Bartlett [ ] and Pople have both demonstrated [M], there is a close relationship between the MPPT/MBPT and CC methods when the CC equations are solved iteratively starting with such an MPPT/MBPT-like initial guess for these double-excitation amplitudes. 

Pople J 2000 webpage http //www.chem.nwu.edu/brochure/pople.html... 

Pople made many developments leading to the suite of Gaussian oomputer oodes that now oonstitute the most widely used eleotronio struoture oomputer programs... 

Pople J A, Krishnan R, Sehlegel H B and Binkley J S 1978 Eleetron eorrelation theories and their applieation to the study of simple reaetion potential surfaee Int. J. Quantum Chem. 14 545-60... 

Krishnan R and Pople J A 1978 Approximate fourth-order perturbation theory of the electron correlation energy Int. J. Quantum Chem. 14 91-100... 

Pople J A 1973 Theoretical models for chemistry Energy, Structure, and Reactivity ed D W Smith and W B McRae (New York Wiley) p 51-67... 

Pople J A and Beveridge D L 1970 Approximate Moieouiar Orbitai Theory (New York McGraw-Hill)... 

Head-Gordon M and Pople J A 1988 Optimization of wavefunotion and geometry in the finite basis Hartree-Fock method J. Phys. Chem. 92 3063... 

The first theoretical handling of the weak R-T combined with the spin-orbit coupling was carried out by Pople [71]. It represents a generalization of the perturbative approaches by Renner and PL-H. The basis functions are assumed as products of (42) with the eigenfunctions of the spin operator conesponding to values E = 1/2. The spin-orbit contribution to the model Hamiltonian was taken in the phenomenological form (16). It was assumed that both interactions are small compared to the bending vibrational frequency and that both the... 

By employing the angle t defined by f68), the perturbative Hamiltonina H can be formulated in the form completely analogous to the Pople and Longuet-Higgins ansatz [69] ... 

SCF approximation. The indices //, v, A, and o denote four atomic orbital centers, so that the number of such orbitals that needs to be calculated increases proportionally scales with ) N, where N is the number of AOs, This was an intractable task in 1965, so Pople, Santry, and Segal introduced the approximation that only integrals in which = v and J. = o (i.e., li)) would be considered and that, further-... 

However, the CNDO method showed systematic weaknesses that were directly attributable to the approximations outlined above, so that it was superseded by the intermediate m lect of diatomic differential overlap (INDO) method, introduced by Pople, Beveridge, and Dobosh in 1967 [13]. The approximation outlined in Eq. (50) proved to be too severe and was replaced by individual values for the possible different types of interaction between two AOs. These individual values, often designated Cgg, Ggp, Gpp and in the literature, can be adjusted to give better agreement with experiment than was possible for CNDO. However, in INDO the two-center terms remain of the same type as those given in Eqs. (51) and (52) (again, there are many variations). This approximation leads to systematic weaknesses, for instance in treating interactions between lone pairs. 

In order to overcome these weaknesses, Pople and co-workers reverted to a more complete approach that they first proposed in 1965 [14], neglect of diatomic differential overlap (NDDO). In NDDO, all four-center integrals (pv are considered in which p and v are on one center, as are 2 and cr (but not necessarily on the same one as and v). Furthermore, integrals for which the two atomic centers are diEFer-ent are treated in an analogous way to the one-center integrals in INDO, resulting... 

The size of the basis set is, however, only one criterion for judging the level of an ab-initio calculation. The situation is best illustrated by what has become known as a Pople diagram [27], as shown in Figure 7-24. 

Figure 7-24. The Pople diagram . The vertical axis gives the size of the basis set and the horizontal axis the correlation treatment. The basis sets and methods given are chosen from the examples discussed in the text. Their positions on the axes (but not the order) are arbitrary.

Hehre, W.J. Kadom, 1,. Schleyer, P,v,R, Pople, J..A. Ah Initio Molecular Orbital Theory, John Wiley and Sons, New York, 1986... 

Pople, J.A. Beveridge, D.L. Approximate. Molecular Orbital I heory McGraw-Hill, New York. 1970. 

CXDO and INDO were developed by the Pople group at Carnegie Melon University. This group chose parameters based pri-... 

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