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

doi:10.1063/1.5095937

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

J Chem Phys. 2019 Jun 14;150(22):224102. doi: 10.1063/1.5095937.

Authors

James H Thorpe¹, Chris A Lopez², Thanh Lam Nguyen¹, Joshua H Baraban³, David H Bross⁴, Branko Ruscic⁴, John F Stanton¹

Affiliations

¹ The Quantum Theory Project, Department of Chemistry, The University of Florida, Gainesville, Florida 32611, USA.
² Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
³ Department of Chemistry, Ben-Gurion University of the Negev, Be'er-Sheva 8410501, Israel.
⁴ Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.

PMID: 31202223
DOI: 10.1063/1.5095937

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.