The lattice dynamics of bcc and fcc W is studied as a function of pressure using the density-functional linear-response theory. At high pressures and T=0 K, bcc W has a higher enthalpy than the fcc and hcp phases and it develops phonon softening anomalies related to this thermodynamic instability; however, it remains dynamically stable. In contrast, the widely unstable shear modes of fcc W at zero pressure (when HfccW>HbccW) stabilize with increasing pressure before HfccW<HbccW. Hence the thermodynamic and dynamic instabilities are uncorrelated.
BT - Physical Review Letters DA - 09/1007 DO - 10.1103/PhysRevLett.79.2073 IS - 11 LA - eng N2 -The lattice dynamics of bcc and fcc W is studied as a function of pressure using the density-functional linear-response theory. At high pressures and T=0 K, bcc W has a higher enthalpy than the fcc and hcp phases and it develops phonon softening anomalies related to this thermodynamic instability; however, it remains dynamically stable. In contrast, the widely unstable shear modes of fcc W at zero pressure (when HfccW>HbccW) stabilize with increasing pressure before HfccW<HbccW. Hence the thermodynamic and dynamic instabilities are uncorrelated.
PY - 1997 SP - 2073 EP - 2076 ST - Phys. Rev. Lett. T2 - Physical Review Letters TI - Phonon Instabilities in fcc and bcc Tungsten VL - 79 SN - 0031-9007 ER -