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

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Quantum Chemistry

Background:

• The high-accuracy extrapolated ab initio thermochemistry (HEAT) model offers precise molecular energy calculations.
• However, its computational cost limits its application to larger molecular systems.

Purpose of the Study:

• To develop economical modifications of the HEAT model for efficient energy evaluations.
• To assess the accuracy and performance of these modified schemes for thermochemistry and kinetics.

Main Methods:

• Evaluation of several economical modifications to the HEAT model chemistry.
• Designation of two schemes: mHEAT and mHEAT+.
• Comparison of calculated heats of formation and total atomization energies with established methods and experimental data.

Main Results:

• The mHEAT+ scheme achieves near subchemical accuracy (±1 kJ/mol) for heats of formation.
• Substantial reduction in computational cost compared to the full HEAT scheme.
• Initial benchmarks for reaction barriers using mHEAT and mHEAT+ show interesting features.

Conclusions:

• mHEAT and mHEAT+ are pragmatic and efficient alternatives to the full HEAT scheme for larger systems.
• These modified models provide a good balance between accuracy and computational cost.
• The schemes show promise for applications in chemical kinetics.