HIGH-PRESSURE STUDIES OF ELEMENTAL METALS. Kenichi Takemura, National Institute for Research in Inorganic Materials, Namiki 1-1, Tsukuba, Ibaraki 305, JAPAN

Most of the elemental metals have simple structures (bcc, fcc, and hcp) at atmospheric pressure. At high pressures, however, some metals exhibit structural phase transitions into unique low-symmetry crystal structures. One of the reasons for that is a change in the bonding properties from nearly spherical to highly directional ones. The pressure-induced electronic transition plays an important role in stabilizing such low-symmetry structures. As examples I will review the changes in the crystal structures of Cs [1] and Ba [2] under high pressure. Other unique crystal structures will also be presented including the singularity in the hcp structure recently found for Zn [3] and Cd [4].

[1] K. Takemura, O. Shimomura, and H. Fujihisa, Phys. Rev. Lett. 66, 2014

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[2] Takemura K., Phys. Rev. B50, 16238 (1994).

[3] Takemura K., Phys. Rev. Lett. 75, 1807 (1995).

[4] Takemura K., (unpublished).