STRUCTURAL SYSTEMATICS OF THE PRESSURE-INDUCED PHASE TRANSITIONS IN P, As, Sb AND Bi. H. Iwasaki^l), T. Kikegawa²⁾,¹⁾Department of Physics, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525, Japan, ²⁾Photon Factory, National Laboratory for High Energy Physics, Tsukuba, Ibaraki 305, Japan

Based on the results of a series of our diffraction studies on the title elements on laboratory X-ray and synchrotron radiation sources and the results recently reported, it is possible to express the sequence of structural phase transitions observed in them in a unified form as follows:

P A17--- A7 ---- PSC

As A7 ---- PSC ---- dist.BCC(II)---- BCC Sb A7 ---- ---- dist.BCC(I) ---- BCC Bi A7-- mod.PSC-- dist.BCC(I)-------- BCC

Abbreviations used are A17 (orthorhombic layered structure), A7 (rhombohedral layered structure), PSC (primitive-simple-cubic) and BCC (body-centered-cubic). dist.BCC(I) represents the tetragonal structure, which is regarded as a distorted BCC (Iwasaki & Kikegawa, 1990; Chen et al, 1994), dist. BCC(II) the orthorhombic structure regarded as another kind of distorted BCC (Greene et al., 1995) and mod.PSC the monoclinic structure reinterpreted as a modified PSC (Chen et al., 1996).

The table suggests that the dist.BCC and BCC phases will form in P, though relevant pressure is extremely high.

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Greene, R. G., Luo, H. & Ruoff, A. L. (1995). Phys. Rev. B51, 597-600.

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