GROUND-STATE PROPERTIES AND HIGH-PRESSURE PHASE OF BERYLLIUM CHALCOGENIDES BESE, BETE, AND BES

We present an ab initio pseudopotential study within the local density approximation of the ground-state and high-pressure phases of BeSe, B eTe, and BeS. We analyze the zinc-blende, NaCl, CsCl, NiAs, and beta-S n structures. By calculating the total energy, atomic forces, and stre ss tensors we determine the structural parameters (lattice constants, bulk moduli, etc.) of these compounds and the transition pressure from the zinc-blende (B3) to the NiAs (B8) phase. The structural parameter s and transition pressure for BeSe and BeTe compare quite well with re cent experimental results. For BeS our results are predictions.