Mpller-Plesset studies

J. K. Laerdahl, K. Faegri, Jr., L. Visscher, and T. Saue, A fuUy relativistic Dirac-Hartree Fock and second-order Mpller-Plesset study of the lanthanide and actinide contraction, J. Chem. Phys. 109, 10806 (10 pages) (1998). 

Pople, J. A., R. Krishnan, H. B. Schlegel, and J. S. Binkley. 1979. Derivative Studies in Hartree-Fock and Mpller-Plesset Theories. Int. J. Quantum Chem. Quantum Chem. Symp. 13, 225-241. 

H2O molecules at different positions. Second-ordCT Mpller-Plesset perturbation theory (MP2) with a 6-311- -G(d,p) basis set has also been apphed to the study of ONO—O, (H20) (n = 1 or 2) complexes. Koppenol and Klasinc studied the cis and trans con-formers as well as the transition state for torsional motion of ONO—O at the HF/6-31(d) leveP. In their calculations, the trans conformer is slightly more stable than the cis form, and the rotational barrier was thought to be quite high. However, correlated methods (MP2) were also used to study this molecule, and they predict that the cis conformer is more stable than the trans conformer . ... 

To test the MR-CI/BK method used in the present study, the isotropic hfcc s were also calculated with various other methods, e.g. the UHF method, Mpller-Plesset perturbation theory up to the fourth order (MP2 - MP4), Cou-... 

The spectroscopic properties of [Pt(2,2, 6, 2-terpyridine)(C=CR)]+ (R=H, CH2OH, and C6H5) (5.6) were theoretically studied by Zhang et al. [101], The second-order Mpller-Plesset perturbation (MP2) was used to optimize the ground state and the single-excitation configuration interaction (CIS) method was employed to obtain the excited-state structure. The spectroscopic properties of the... 

J. Antony and S. Grimme, Is spin-component scaled second-order Mpller-Plesset perturbation theory an appropriate method for the study of noncovalent interactions in molecules J. Phys. Chem. A, 111 (2007) 4862-4868. 

Accounting for relativistic effects in computational organotin studies becomes complicated, because Hartree-Fock (HF), density functional theory (DFT), and post-HF methods such as n-th order Mpller-Plesset perturbation (MPn), coupled cluster (CC), and quadratic configuration interaction (QCI) methods are non-relativistic. Relativistic effects can be incorporated in quantum chemical methods with Dirac-Hartree-Fock theory, which is based on the four-component Dirac equation. " Unformnately the four-component Flamiltonian in the all-electron relativistic Dirac-Fock method makes calculations time consuming, with calculations becoming 100 times more expensive. The four-component Dirac equation can be approximated by a two-component form, as seen in the Douglas-Kroll (DK) Hamiltonian or by the zero-order regular approximation To address the electron cor-... 

A very detailed study of the THG nonlinear susceptibilities of four polymorphs of ice (Dl, II, VIII, and IX) was carried out by Reis et al. [108] at the second-order Mpller Plesset perturbation theory level of approximation. The... 

So far, this method has only been applied to one-dimensional periodic systems, but, except for the involved coding, there is no perceived difficulty to extend it to three-dimensional crystals. As shown by studies on oligomers, these TDHF results suffer from the lack of electron correlation which can modify estimates by as much as one order of magnitude. Generalizing this approach by using traditional electron correlation methods (Mpller Plesset and coupled-cluster) or ad hoc DFT treatments is therefore a step to be pursued. 

As has been demonstrated by numerous studies, the accuracy of properties calculated using the GGA DFT methods is, in most cases, comparable to or better than those from ab initio MP2 (Mpller-Plesset second-order perturbation) or CISD (configuration interaction with single and double excitations) methods. In fact, the accuracy of the DFT results in some instances matches those obtained from the much more costly (but, in principle, more exact) CCSD(T) (coupled cluster singles and doubles with a perturbative inclusion of connected triple excitations) method (29) and the ab initio G1 procedure (30). 

The dimers of Be, Mg and Ca are very weakly bound by the electron correlation effects, at the self-consistent field (SCF) level they are not stable. The binding energy of alkaline earth dimers is only 2-4 times larger than that in Kr2 and Xe2 dimers. Thus, alkaline dimers can be attributed to the van der Waals molecules. The situation is changed in many-atom clusters, even in trimers (Table II). This is evidently a manifestation of the many-body effects. The crucial role of the 3-body forces in the stabilization of the Be clusters was revealed at the SCF level previously [3-5], and more recently was established at the Mpller-Plesset perturbation theory level up to the fourth order (MP4) [6,7]. The study of binding in the Ben clusters [8-10] reveals that the 3-body exchange forces are attractive and give an important contribution to... 

Nonadditive effects in open-shell clusters have been investigated only recently and relatively little information is available on their importance and physical origin. From the theoretical point of view, open-shell systems are more difficult to study since the conventional, size-consistent computational tools of the theory of intermolecular forces, like the Mpller-Plesset perturbation theory, coupled cluster theory, or SAPT, are less suitable or less developed for applications to open-shell systems than to closed-shell ones. Moreover, there are many types of qualitatively different open-shell states, exhibiting different behavior and requiring different theoretical treatments. 

---