Interplay of Mechanochemistry and Material Processes in the Graphite to Diamond Phase Transformation

TL;DR

This study uses steered molecular dynamics to explore how out-of-plane strains influence the graphite-to-diamond phase transformation, revealing that such strains lower transformation thresholds but also slow the overall process due to defect formation changes.

Contribution

It demonstrates how out-of-plane strains affect phase transformation pathways and kinetics in graphite, providing new insights into mechanochemical effects in condensed matter.

Findings

Out-of-plane strain reduces the compressive strain needed for phase transformation.

Altered defect formation processes influence the transformation kinetics.

The combined work has a local minimum, affecting transformation efficiency.

Abstract

he manifestation of intra-molecular strains in covalent systems is widely known to accelerate chemical reactions and open alternative reaction paths. This process is moderately understood for isolated molecules and uni-molecular processes. However, in condensed matter processes such as phase transformations, material properties and structure may influence typical mechanochemical effects. Therefore, we utilize steered molecular dynamics to induce out of plane strains in graphite and compress the system under a constant strain rate to induce phase transformation. We show that the out of plane strain allows for phase transformations to initiate at lower amounts of compressive strain. Yet, in contrast to typical mechanochemical results, the sum of compressive and out of plane work needed to form diamond has a local minimum due to altered defect formation processes during phase transformation. Additionally, these altered processes slow the kinetics of the phase transformation, taking longer from initiation to total material transformation.