To allow direct comparison to our AIMD reference results, we first compute K with the same method, namely the finite strain difference method. All simulations were performed in the (N, V, T ) ensemble to enforce a volume V and compute the resulting pressure P (V ) of the equilibrated system. The reduced computational cost allowed for smoother volumetric deformations (1.5% change over 100 ps) and a longer equilibration (100 ps, shown on Figure ) than was possible with AIMD.