  The high entropy alloy containing refractory metals Mo-Nb-Ta-W has a body
centered cubic structure, which is not surprising given the complete mutual
solubility in BCC solid solutions of all pairs of the constituent elements.
However, first principles total energy calculations for the binaries reveal a
set of distinct energy minimizing structures implying the likelihood of
chemically ordered low temperature phases. We apply a hybrid Monte Carlo and
molecular dynamics method to evaluate the temperature-dependent chemical order.
At 300K a cesium-chloride ordering emerges between mixed (Nb,Ta) sites and
mixed (Mo,W) sites. This order is lost at elevated temperatures.
