The performance of a variety of high-level composite procedures, as well as lower-cost density functional theory (DFT)- and second-order perturbation theory (MP2)-based methods, for the prediction of absolute and relative R-X bond dissociation energies (BDEs) was examined for R = Me, Et, i-Pr and t-Bu, and X = H, CH(3), OCH(3), OH and F. The methods considered include the high-level G3(MP2)-RAD...

Short-Range Correlation Models in Electronic Structure Theory by Matthew Bryant Goldey Doctor of Philosophy in Chemistry University of California, Berkeley Professor Martin Head-Gordon, Chair Correlation methods within electronic structure theory focus on recovering the exact electronelectron interaction from the mean-field reference. For most chemical systems, including dynamic correlation, th...

the use of appropriate level of theories for studying weak interactions such as 8-8 stackinginteractions of aromatic molecules has been an important aspect, since the high level methods havelimitations for application to large molecules. the differences in the stacking energies of variousaromatic molecular structures are found significant. it is also very important for identifying the mostfavor...

The performances of Møller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT) have been assessed for the purposes of investigating the interaction between stannylenes and aromatic molecules. The complexes between SnX2 (where X = H, F, Cl, Br, and I) and benzene or pyridine are considered. Structural and energetic properties of such complexes are calculated using ...

The use of appropriate level of theories for studying weak interactions such as 8-8 stackinginteractions of aromatic molecules has been an important aspect, since the high level methods havelimitations for application to large molecules. The differences in the stacking energies of variousaromatic molecular structures are found significant. It is also very important for identifying the mostfavor...

Moller-Plesset second-order (MP2) perturbation theory remains the least expensive standard ab initio method that includes electron correlation, scaling as O(N5) with the number of molecular orbitals N. Unfortunately, when restricted Hartree-Fock orbitals are employed, the potential energy curves calculated with this method are of little use at large interatomic separations because of the diverg...

Two modifications of Gaussian-4 (G4) theory [L. A. Curtiss et al., J. Chem. Phys. 126, 084108 (2007)] are presented in which second- and third-order perturbation theories are used in place of fourth-order perturbation theory. These two new methods are referred to as G4(MP2) and G4(MP3), respectively. Both methods have been assessed on the G3/05 test set of accurate experimental data. The averag...

Machine-learned potential energy surfaces (PESs) for molecules with more than 10 atoms are typically forced to use lower-level electronic structure methods such as density functional theory and second-order Moller-Plesset perturbation (MP2). While these efficient realistic, they fall short of the accuracy ``gold standard'' coupled-cluster method, especially respect reaction isomerization barrie...

Three major conformations of H(2)S-benzene dimer have been located with a variety of density functional theories (DFT) and second order Møller-Plesset perturbation (MP2). In line with an experiment, MP2 results indicate that the tilted C(s)-symmetry structure is a stable dimer, yet a C(2v)-symmetry structure is only a second-order saddle point. Although all of the examined DFT methods also pred...