  We have performed experimental and theoretical studies of the structural
stability of YAsO4 and YCrO4 at high pressures. X-ray diffraction experiments
together with ab initio total-energy and lattice-dynamics calculations have
allowed us to completely characterize a pressure-induced structural phase
transition from the zircon to the scheelite structure in both compounds.
Furthermore, total-energy calculations have been performed to check the
relative stabilities of different candidate structures at different pressures
and allow us to propose for YAsO4 the zircon \rightarrow scheelite \rightarrow
SrUO4-type sequence of structures. In this sequence, sixfold arsenic
coordination is attained for the SrUO4-type structure above 32 GPa. The whole
sequence of transitions is discussed in comparison with YVO4, YPO4, YNbO4,
YMoO4, and YTaO4. Also a comparative discussion of lattice-dynamics properties
is presented. The band-gap for YAsO4 and YCrO4 and band structure for YAsO4 are
also reported. Finally, the room-temperature equation of state of different
compounds is also obtained.
