High-accuracy extrapolated ab initio thermochemistry. IV. A modified recipe for computational efficiency

James H. Thorpe, Chris A. Lopez, Thanh Lam Nguyen, Joshua H. Baraban, David H. Bross, Branko Ruscic, John F. Stanton

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33 Scopus citations

Abstract

A number of economical modifications to the high-accuracy extrapolated ab initio thermochemistry (HEAT) model chemistry are evaluated. The two resulting schemes, designated as mHEAT and mHEAT+, are designed for efficient and pragmatic evaluation of molecular energies in systems somewhat larger than can be practically studied by the unapproximated HEAT scheme. It is found that mHEAT+ produces heats of formation with nearly subchemical (±1 kJ/mol) accuracy at a substantially reduced cost relative to the full scheme. Total atomization energies calculated using the new thermochemical recipes are compared to the results of the HEAT-345(Q) model chemistry, and enthalpies of formation for the three protocols are also compared to Active Thermochemical Tables. Finally, a small selection of transition states is studied using mHEAT and mHEAT+, which illuminates some interesting features of reaction barriers and serves as an initial benchmark of the performance of these model chemistries for chemical kinetics applications.

Original languageEnglish
Article number224102
JournalJournal of Chemical Physics
Volume150
Issue number22
DOIs
StatePublished - 14 Jun 2019

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