First-principles search for high-pressure phases of GaAsO4

First-principles calculations are performed to examine the high-pressure be havior of the berlinite system GaAsO4. Structural properties of six possibl e GaAsO4 phases, berlinite, VCrO4, rutile, AlNbO4, BiSbO4 and a monoclinic structure with space group P2(1)/m11, are investigated up to 25 GPa. It is shown that between 1.4 and 2.3 GPa, a monoclinic AlNbO4-type structure is e nergetically favored, and beyond this range the favored structure is a ruti le form. We also identify an unexpected metastable form of rutile structure (rutile-II) produced as a high-pressure modification of the VCrO4-type str ucture. [S0163-1829(99)01529-5].