Adsorption of parahydrogen on graphene

TL;DR

This study uses Quantum Monte Carlo simulations to explore the low-temperature phases of parahydrogen adsorbed on graphene, revealing phase behaviors similar to helium and evidence of second-layer promotion.

Contribution

It provides the first detailed phase diagram of parahydrogen on graphene, highlighting new incommensurate phases and second-layer promotion phenomena.

Findings

Phase diagram similar to helium on graphene

Identification of commensurate and domain wall phases

Observation of second-layer promotion at high coverage

Abstract

We study the low temperature properties of a single layer of parahydrogen adsorbed on graphene, by means of Quantum Monte Carlo simulations. The computed phase diagram is very similar to that of helium on the same substrate, featuring commensurate solid phases with fillings 1/3 and 7/16, as well as domain wall phases at intermediate coverages. At higher coverage the system transitions to an incommensurate, compressible phase. Evidence of promotion of molecules to the second layer is observed at a coverage close 0.112 inverse square Angstroms, significantly above existing theoretical estimates.