High-throughput calculations of pressure-induced phase transitions in tungsten nitride

We have previously\footnote{M. Mehl {\em et al.}, arXiv:1403.2762 [cond-mat.mtrl-sci] (2014)} used high-throughput electronic structure calculations\footnote{S. Curtarolo {\em et al.}, http://materials.duke.edu/aflow.html} to determine the ground state structures of the tungsten-nitride system as a function of composition. In doing this, we found many structures with are close to the W-N convex hull and apparently metastable. The question then arises if any of these structures can be stabilized under pressure. To test this, we have determined the ground state hull as a function of pressure up to 50~GPa. We find that the structures on the hull change with pressure. We discuss some of the more interesting structures, and show how the choice of density functional changes our predictions.