We have calculated the thermochemistry and rate coefficients for stable molecules and reactions in the title reaction families using CBS-QB3 and B3LYP/CBSB7 methods. The accurate treatment of hindered rotors for molecules having multiple internal rotors with potentials that are not independent of each other can be problematic, and a simplified scheme is suggested to treat them. This is particul...

We develop and validate a density functional, XYG3, based on the adiabatic connection formalism and the Görling-Levy coupling-constant perturbation expansion to the second order (PT2). XYG3 is a doubly hybrid functional, containing 3 mixing parameters. It has a nonlocal orbital-dependent component in the exchange term (exact exchange) plus information about the unoccupied Kohn-Sham orbitals in ...

The need of a concerted multi-disciplinary approach in the investigation of intermetallic systems and the role of thermochemistry are underlined. The activity carried out in the Author’s laboratory in the alloy thermodynamics is summarized. The different instruments (calorimeters) built in laboratory are briefly presented and their performance discussed. The results obtained in the measurement ...

Effects of increased basis-set size as well as a correlated treatment of the diagonal Born-Oppenheimer approximation are studied within the context of the high-accuracy extrapolated ab initio thermochemistry (HEAT) theoretical model chemistry. It is found that the addition of these ostensible improvements does little to increase the overall accuracy of HEAT for the determination of molecular at...

The exchange hole, which is one of the principal constituents of the density functional formalism, can be used to design accurate range-separated hybrid functionals in association with appropriate correlation. In this regard, the exchange hole derived from the density matrix expansion has gained attention due to its fulfillment of some of the desired exact constraints. Thus, the new long-range ...

A scheme is presented for calculating the heats of formation of adsorbed species on metal surfaces using only two pieces of gas phase data, both of which are available from either theory or experiment. Using this quasiempirical valence bond (QVB) approach, heats of adsorption and adsorbate-surface bond strengths can be estimated, yielding predictions of surface thermochemistry and reaction mech...

High accuracy ab initio methods for computational thermochemistry have been applied to aluminum compounds expected to be present during combustion of aluminum particles. The computed enthalpies of formation at 298.15 K agree well with experimental values from the literature for AlCl, AlCl3, AlO, AlOAl, linear OAlO, planar Al2O2, AlOH, AlH, and AlN. The agreement is fair for AlCl2. Major revisio...

Density functional theory (DFT) is often used to determine the electronic and geometric structures of molecules. While studying alkynyl radicals, we discovered that DFT exchange-correlation (XC) functionals containing less than ∼22% Hartree-Fock (HF) exchange led to qualitatively different structures than those predicted from ab initio HF and post-HF calculations or DFT XCs containing 25% or mo...