First-principles search for high-pressure phases of GaAsO₄

First-principles calculations are performed to examine the high-pressure behavior of the berlinite system GaAsO₄. Structural properties of six possible GaAsO₄ phases, berlinite, VCrO₄, rutile, AlNbO₄, BiSbO₄ and a monoclinic structure with space group P2₁/m11, are investigated up to 25GPa. It is shown that between 1.4 and 2.3 GPa, a monoclinic AlNbO₄-type structure is energetically favored, and beyond this range the favored structure is a rutile form. We also identify an unexpected metastable form of rutile structure (rutile-II) produced as a high-pressure modification of the VCrO₄-type structure.