Gaussian-1 theory: A general procedure for prediction of molecular energies

Abstract

A general procedure is developed for the computation of the total energies of molecules at their equilibrium geometries. Ab initio molecular orbital theory is used to calculate electronic energies by a composite method, utilizing large basis sets (including diffuse-sp, double-d and f-polarization functions) and treating electron correlation by Mo/ller–Plesset perturbation theory and by quadratic configuration interaction. The theory is also used to compute zero-point vibrational energy corrections. Total atomization energies for a set of 31 molecules are found to agree with experimental thermochemical data to an accuracy greater than 2 kcal mol−1 in most cases. Similar agreement is achieved for ionization energies, electron and proton affinities. Residual errors are assessed for the total energies of neutral atoms.

Long-range corrected hybrid density functionals with damped atom–atom dispersion corrections

“…[18], that contains 412 accurate experimental and accurate theoretical results, including the 18 atomic energies from the H atom to the Ar atom [44], the atomization energies (AEs) of the G3/99 set [45][46][47] (223 molecules), the ionization potentials (IPs) of the G2-1 set [48] (40 molecules, excluding SH 2 ( 2 A 1 ) and N 2 ( 2 Π) cations due to the known convergence problems for semilocal density functionals [46]), the electron affinities (EAs) of the G2-1 set (25 molecules), the proton affinities (PAs) of the G2-1 set (8 molecules), the 76 barrier heights (BHs) of the NHTBH38/04 and HTBH38/04 sets [49,50], and the 22 non-covalent interactions of the S22 set [51]. To prevent the double-counting of total energy from the KS-DFT and the dispersion corrections, all the parameters in ωB97X-D, are determined self-consistently by a leastsquares fitting procedure described in Ref.…”

Using CIPSI Nodes in Diffusion Monte Carlo

“…(11). A reduction of the computational cost occurs only when a full line (↑) or a full column (↓) of C contains only zeroes, in that case the determinant D σ can be removed from the calculation.…”

Characterization of Reaction Pathways on the Potential Energy Surfaces for H + SO2 and HS + O2

“…17 Morris and Jackson 18 characterized HSO 2 and HOSO at the MP4/DZP//MP2/DZP level, while we have published an investigation of these two molecules plus HSOO and HOOS carried out with Gaussian-2 (G2) theory, and focused on their thermochemistry. 19 The G2 methodology has a target accuracy of (8 kJ mol -1 for atomization enthalpies and an average absolute deviation of 5 kJ mol -1 for a set of 55 test molecules [20][21][22] and yields approximate QCISD(T)/6-311+G-(3df,2p) energies. These results for bound minima were combined with empirically estimated barrier heights in a recent flame mechanism by Glarborg et al 23 Very recently, Qi et al published MP2/6-311G(d,p) values for the geometries, frequencies, and energies in the H + SO 2 system 24 and Tureček et al 11 used G2(MP2) theory to investigate neutral and ionic HSO 2 species and transition states.…”