This study explores the degree to which GGA, meta-GGA, hybrid GGA, and hybrid meta-GGA functionals of density functional theory (DFT), when used with the 6-31+G(d) basis set, are able to reproduce the MP2/6-31+G(d) structures and energetics of the species involved in the reactions of halomethyllithium carbenoids with ethylene. While many popular DFT functionals have been parametrized and/or ben...

Background. The honey bee (Apis mellifera) is the most important pollinator in agriculture worldwide. However, the number of honey bees has fallen significantly since 2006, becoming a huge ecological problem nowadays. The principal cause is CCD, or Colony Collapse Disorder, characterized by the seemingly spontaneous abandonment of hives by their workers. One of the characteristics of CCD in hon...

Description: Tables of cartesian coordinates optimized at MP2 level and the total energies computed at CCSD(T) level of all species mentioned in the text and influence of basis sets Table S-I. Selected geometrical parameters a for structures 1-10 calculated with different theoretical methods Structure Geometrical parameters b HF MP2 BP86 B3LYP

Coupled-cluster theory with single and double excitations (CCSD) is a promising ab initio method for the electronic structure of three-dimensional metals, which second-order perturbation (MP2) diverges in thermodynamic limit. However, due to high cost poor convergence CCSD respect basis size, applying periodic systems often leads large set errors. In common "composite" method, MP2 used recover ...

Ab initio electronic structure calculations with RHF, MP2, and CCSD(T) wave functions have been used to investigate a reaction path for the hydrosilation reaction catalyzed by divalent titanium (modeled by TiH2). Optimized structures and energies are presented. All levels of theory predict a barrierless reaction path compared to a barrier of 78 kcal/mol for the uncatalyzed reaction. The use of ...

Predicting accurate bond length alternations (BLAs) in long conjugated oligomers has been a significant challenge for electronic-structure methods for many decades, made particularly important by the close relationships between BLA and the rich optoelectronic properties of π-delocalized systems. Here, we test the accuracy of recently developed, and increasingly popular, double hybrid (DH) funct...

The development of new technologies has an impact on a better understanding of the components present in inter/circum-stellar space and also of the interactions of different species.[1] That is one of Astrochemistry focus, and it is a challenge for the scientists, even more due to the limited access and knowledge on that characteristic environment. [2,3] Therefore, the study of interactions bet...

We present a reduced scaling and exact reformulation of state specific complete active space second-order perturbation (CASPT2) analytical gradients in terms the MP2 Fock derivatives using supporting subspace method. This work follows naturally from formulation CASPT2 energy dressed orbitals builds. For given configuration, corresponding to MP2-gradient can be evaluated with O(N5) operations, w...

Using a Lagrangian-based approach, we present a more elegant derivation of the equations necessary for the variational optimization of the molecular orbitals (MOs) for the coupled-cluster doubles (CCD) method and second-order Møller-Plesset perturbation theory (MP2). These orbital-optimized theories are referred to as OO-CCD and OO-MP2 (or simply "OD" and "OMP2" for short), respectively. We als...