Fourth-order Moller-Plesset

These integrals will he non-zero only for double excitations, according to the Brillouin theorem. Third- and fourth-order Moller-Plesset calculations (MP3 and MP4) are also... 

Higher level calculations, based on higher orders of Moller-Plesset perturbation theory, can also be performed, albeit with the consumption of much more computer time. For example, an MP4SDTQ calculation uses fourth-order Moller-Plesset perturbation theory, includes excitations through quadruples, and gives better energies than MP2 does. 

BP86/TZ2P (nonlocal DFT with the Becke-88-Perdew-86 functional). cMP4SDQ/6-31+G (fourth-order Moller-Plesset perturbation theory with single, double, and quadruple excitations). 

S. S b0 and P. Pulay,/. Chem. Phys., 86, 914 (1987). Fourth-Order Moller-Plesset Perturbation Theory in the Local Correlation Treatment. I. Method. 

These NMR results are consistent with MO calculations performed independently by Koch et al. (1988) and by the joint groups of Saunders, Schindler, Schleyer and Wiberg (Schleyer et al., 1988) at the MP2/6-31G and higher levels of theory (full fourth-order Moller-Plesset perturbation theory ). The C4Hf-system consists, in the light of these calculations, of a cyclobutyl cation (better described as a nonclassical pentacoordinated bicyclobutanonium ion, 7.135) and a bisected cyclopropyl cation (7.132) with an isomerization barrier of 2.5 kJ mol ... 

G basis sets and geometry optimizations by fourth-order Moller-Plesset calculations. Analogously, the dediazoniation of 2-diazoacetaldehyde was studied. We discussed further theoretical investigations on carbene formation in Section 5.4 in the context of comparisons of diazomethane with diazirine (e.g., Yamamoto et al., 1994). 

Theoretically calculated formation enthalpies from fourth-order Moller-Plesset theory (MP4) are to be preferred to these latter estimates [16], namely AfHo = 35.7 and = 34.8 2 [16], 37.3 [17], and 33.4 (139.8 kJ/mol) [18] (atomic data were taken from [19], where white P is used as the reference state). 

The best estimate of the binding energy, after correction of this error [60], is approximately 23 kJ/mol, 5 of which are associated with electron correlation. Del Bene s recent calculation [36], which employed a 6-31 +G(2 /, 2p) basis set and full fourth-order Moller-Plesset treatment of correlation, found a value of 28 kJ/mol (although superposition error was not removed). Within the context of hydrides of first-row atoms, this complex is the most weakly bound, with the order as follows ... 

Ab initio molecular orbital theory at the HF/6-31G level has been used to investigate the structure of Lewis acid/base adducts of boron hydrides with argon and a variety of substrates that may be encountered in the mechanism for the oxidation of diborane. By use of fourth-order Moller-Plesset theory, i.e., MP4SDTQ, correlation effects are calculated at the HF/6-31G geometries. From HF/6-31G calculations, the following distances (in A) and angles for Ar-boron hydride adducts were found [22] ... 

LDA - Local Density Approximation, N-LDA - gradient corrected LDA, (U)HF - (Unrestricted) Hartree-Focl CIS(D) - Configuration Interaction including Single (and Double) excitations, MP2(3 or 4) - second (third or fourth) order Moller-Plesset perturbation theory, MBPT - Ntoy Body Perturbation Theory... 

Ab initio calculations using the fourth-order Moller-Plesset perturbation theory (MP4(SDTQ)) were performed on HeN " in its ground (X IT) and excited states ( X ) which both were found to be covalently bound. HeN is metastable and dissociates via the exothermic charge-separation reactions HeN (X Il) He ( S) + N ( P) and HeN (" 2 ) He ( S) + N ( D). There is a barrier to dissociation of 201.7 kJ/mol for ground-state HeN. Other calculated data are [1] ... 

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