Ab initio intermolecular interactions mediate thermochemically real-fluid effects that affect system reactivity

TL;DR

This paper demonstrates that ab initio multi-body intermolecular potentials significantly improve the accuracy of modeling supercritical fluid properties and reactivity, especially autoignition delay times, over traditional empirical approaches.

Contribution

The study introduces a new framework incorporating ab initio multi-body intermolecular potentials into supercritical fluid modeling, revealing their critical role in thermochemical and kinetic predictions.

Findings

Empirical potentials can cause significant errors in supercritical fluid modeling.

Ab initio potentials accurately describe real-fluid effects in combustion.

Radical and multi-body interactions greatly influence autoignition delay times.

Abstract

The properties of supercritical fluids are dictated by intermolecular interactions that involve two or more molecules. Such intermolecular interactions were described via intermolecular potentials in historical supercritical combustion modeling studies, but have been treated empirically and with no consideration of radical interactions or multi-body interactions involving more than two molecules. This approach has been adopted long ago, assuming sufficient characterization of real-fluid effects during supercritical combustion. Here, with data from ab initio multi-body intermolecular potentials, non-empirical Virial Equation of State (EoS), and real-fluid thermochemical and kinetic simulations, we reveal that empirical intermolecular potentials can lead to significant errors in representing supercritical fluids under common combustion situations, which can be impressively described by ab initio intermolecular potentials. These interactions are also found to greatly influence autoignition delay times, a common measure of global reactivity, with significant contributions from radical interactions and multi-body interactions. It is therefore of necessity to incorporate ab initio intermolecular interactions in studying supercritical combustion and various dynamic systems involving supercritical fluids, which has now been enabled through the new framework developed in the present study.