Test of a simple and flexible molecule model for alpha-, beta- and gamma-S8 crystals

TL;DR

This paper uses molecular dynamics simulations with a simple, flexible molecule model to analyze the phase diagram of S8 crystals, including alpha, beta, and gamma phases, capturing structural phase transitions.

Contribution

It introduces a molecular dynamics approach with a flexible molecule model to study S8 crystal phases and their phase transitions.

Findings

Successfully reproduces known phase transitions of S8 crystals.

Provides insights into the structural differences among alpha, beta, and gamma S8.

Demonstrates the model's capability to simulate orientational order and disorder.

Abstract

S8 is the most stable compound of elemental sulfur in solid and liquid phases, at ambient pressure and below 400K. Three crystalline phases of S8 have been clearly identified in this range of thermodynamic parameters, although no calculation of its phase diagram has been performed yet. alpha- and gamma-S8 are orientationally ordered crystals while beta-S8 is measured as orientationally disordered. In this paper we analyze the phase diagram of S8 crystals, as given by a simple and flexible molecule model, via a series of molecular dynamics (MD) simulations. The calculations are performed in the constant pressure- constant temperature ensemble, using an algorithm that is able to reproduce structural phase transitions.