Development and validation of a parameter-free model chemistry for the computation of reliable reaction rates

TL;DR

This paper introduces a modified, parameter-free model chemistry called jun-Cheap that accurately computes reaction rates for astrochemical and atmospheric processes, outperforming existing methods without empirical parameters.

Contribution

The paper presents a refined, parameter-free model chemistry that achieves high accuracy in reaction rate calculations, suitable for complex astrochemical and atmospheric reactions.

Findings

Outperforms well-known model chemistries in accuracy

Achieves sub-chemical accuracy without empirical parameters

Computationally efficient for large-scale reaction rate calculations

Abstract

A recently developed model chemistry (jun-Cheap) has been slightly modified and proposed as an effective, reliable and parameter-free scheme for the computation of accurate reaction rates with special reference to astrochemical and atmospheric processes. Benchmarks with different sets of state-of-the-art energy barriers spanning a wide range of values show that, in the absence of strong multi-reference contributions, the proposed model outperforms the most well-known model chemistries, reaching a sub-chemical accuracy without any empirical parameter and with affordable computer times. Some test cases show that geometries, energy barriers, zero point energies and thermal contributions computed at this level can be used in the framework of the master equation approach based on ab-initio transition state theory (AITSTME) for obtaining accurate reaction rates.