Deciphering Interstellar Ice Morphology: Atomistic Simulations Reveal the Complex Behavior of Ethanethiol

TL;DR

This study uses atomistic simulations to explore the behavior and phase transitions of ethanethiol ice on interstellar dust analogs, revealing complex morphology and melting properties relevant to astrochemistry.

Contribution

It provides the first detailed atomistic simulation insights into ethanethiol's phase behavior and morphology at low temperatures in interstellar conditions.

Findings

Amorphous ethanethiol does not spontaneously crystallize upon heating.

Ethanethiol ice crystals melt at elevated temperatures on KBr substrate.

No reversible phase change observed in thin ice samples.

Abstract

Ethanethiol (C$_2$H$_5$SH), a molecule detected in the interstellar medium (ISM), indicates the rich chemistry involving sulfur atoms. However, its behavior at low temperatures remains elusive, particularly the reported transition from an amorphous phase to a crystal. This study employs classical molecular dynamics (MD) simulations to reproduce the liquid-state properties of ethanethiol and to simulate the initial amorphous state of ethanethiol films deposited on a KBr substrate. The amorphous ethanethiol did not show spontaneous crystallization upon increasing temperature. Also, ethanethiol ice crystals exhibit melting behavior on KBr substrate at elevated temperatures. Our MD simulations of thin ice samples do not show any signature reversible phase change. It will be interesting to continue this study with a thicker sample, which is beyond our current computational means. These findings underscore the complexity of icy mantle morphology on cold ISM dust grains.