Phase-Transition Studies of Germanium to 1.25 Mbar

Yogesh K. Vohra; Keith E. Brister; Serge Desgreniers; Arthur L. Ruoff; K. J. Chang; Marvin L. Cohen

doi:10.1103/PhysRevLett.56.1944

Phase-Transition Studies of Germanium to 1.25 Mbar

Yogesh K. Vohra, Keith E. Brister, Serge Desgreniers, Arthur L. Ruoff, K. J. Chang, and Marvin L. Cohen

Phys. Rev. Lett. 56, 1944 – Published 5 May 1986

Abstract

New phase transitions in Ge were observed by energy-dispersive x-ray diffraction techniques for pressures up to 125 GPa (1.25 Mbar) as follows: the $β$ -Sn structure to the simple hexagonal (sh) phase at 75 ± 3 GPa and to the double hexagonal close-packed structure (dhcp) at 102 ± 5 GPa. These are the highest pressures for which a crystalline structure change has been directly observed by x-ray diffraction. Total-energy pseudopotential calculations predict 84 ± 10 GPa for the $β$ -Sn to sh phase transition and 105 ± 2 GPa for sh to hcp (not dhcp) transition. The role of 3 $d$ core electrons in increasing the transformation pressures in Ge, as compared to Si, is emphasized.

Received 16 December 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.1944

Authors & Affiliations

Yogesh K. Vohra, Keith E. Brister, Serge Desgreniers, and Arthur L. Ruoff

Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853

K. J. Chang and Marvin L. Cohen

Department of Physics, University of California, Berkeley, California 94720
Materials and Molecular Research Division, Lawrence Berkeley Laboratory, Berkeley, California 94720