Pressure and temperature effects on the Gamma and N-phonons in zirconium

The effective potentials for the E-2g-phonon at the Gamma point of the Bril louin zone of hcp Zr and the transverse N phonon of bcc Zr are calculated f or different pressures by the frozen-phonon method. The temperature and pre ssure dependences of the phonon frequencies are studied within the framewor k of a modified pseudo-harmonic approximation. The results obtained are in good agreement with the experimental ones. The change observed in the behav ior of frequencies with increasing temperature and pressure may be attribut ed to the peculiarities of the phase diagram of zirconium. (C) 2000 Elsevie r Science B.V. All rights reserved.