Structure change, layer sliding, and metallization in high-pressure MoS$_{2}$

TL;DR

This study uses ab initio and metadynamics simulations to predict that MoS2 becomes metallic under high pressure, undergoes a structural layer sliding transition, and may eventually become superconducting at ultrahigh pressures.

Contribution

It is the first to identify the layer sliding transition and structural change in MoS2 under high pressure, explaining previous experimental observations.

Findings

MoS2 metallizes above 20-30 GPa

Layer stacking changes from 2H_c to 2H_a during transition

Superconductivity may occur at ultrahigh pressures

Abstract

Based on ab initio calculations and metadynamics simulations, we predict that 2H-MoS$_2$, a layered insulator, will metallize under pressures in excess of 20-30 GPa. In the same pressure range, simulations and enthalpy optimization predict a structural transition. Free mutual sliding of layers takes place at this transition, the original 2H$_c$ stacking changing to a 2H$_a$ stacking typical of 2H-NbSe$_2$, an event explaining for the first time previously mysterious X-ray diffraction and Raman spectroscopy data. Phonon and electron phonon calculations suggest that pristine MoS$_2$, once metallized, will require ultrahigh pressures in order to develop superconductivity.