要旨：
The combination of high-resolution synchrotron x-ray diffraction,
optical spectroscopies, and large hydrostatic pressures produced by
diamond anvil cells offers a unique approach to studying
structural, vibrational, and band structure related properties of
solids. Since the introduction of the DAC, high pressure investigations
of oxide materials have remained at the forefront of experimental high
pressure research. This talk will be concerned with recent pressure
studies of phase transitions in oxides [1-4] which have in common a low
coordination of their ambient pressure phases. Topics to be discussed
are the rich PT phase diagram of the spin-Peierls compound CuGeO$_3$
and new insights into pressure-induced amorphization of berlinite-type
compounds, as obtained from combined x-ray diffraction, optical
spectroscopy and Moessbauer studies.
[1] A. R. Goni et al., Phys. Rev. Lett. 77, 1079 (1996).
[2] S. Braeuninger et al., Phys. Rev. B 56, R11357 (1997).
[3] M. P. Pasternak et al., Phys. Rev. Lett. 79, 4409 (1997).
[4] T. Zhou et al., Phys. Rev. B 57, Jan. 1, 1998.