  Metal hydrides are promising candidates for hydrogen storage applications.
From a materials discovery perspective, an accurate, efficient computational
workflow is urgently required that can rapidly analyze/predict thermodynamic
properties of these materials. The authors have recently introduced a
thermodynamic property calculation framework based on the lattice reverse Monte
Carlo (RMC) method. Here the approach is extended to metal hydrides, which
exhibit significant volume expansion, strong interaction between hydrogen and
the host atoms, lattice strain, and a phase transition. We apply the technique
to the nickel hydride (NiH_x) system by calculating the
pressure-composition-temperature (PCT) isotherm and constructing its phase
diagram. An attractive feature of our approach is that the entire phase diagram
can be accurately constructed in few minutes by considering <10 configurations.
In contrast, a popular technique based on grand canonical Monte Carlo would
require sampling of several million configurations. The computational workflow
presented paves the way for the approach to be used in future for wider
materials search and discovery.
