Comment on Zarechnaya et al. Pressure-induced isostructural phase transformation in gamma-B28. Phys. Rev. B 82, 184111 (2010)

Zarechnaya et al. claimed an isostructural transformation in gamma-B28 at about 40 GPa; below which the phase is more compressible (B0=227 GPa) and above which less compressible (B0=281 GPa) than in previous experiments or theory. Here we wish to point out some interesting questions related to these claims. Summarizing briefly our points, the suggestion of an isostructural transformation is inconsistent with ab initio calculations and experiment, we see no physical mechanism that could be responsible for such a transformation, and the evidence for it is self-contradictory.