High-pressure x-ray-absorption study of GaSe

We performed two x-ray-absorption experiments under pressure in GaSe, at the Ga and Se K edges (10.368 and 12.653 keV, respectively), up to 34 GPa. The Ga-Se distance obtained from the extended x-ray-absorption fine-structure tit decreases monotonically up to 16′ 2 GPa, following a first-order Murnaghan equation of state with B 0 =92′6 GPa and B' 0 fixed to 5. Under a plausible hypothesis, we calculate the evolution of the whole structure up to 16′2 GPa. These calculations indicate that the layer thickness decreases slightly under pressure.