Pressure dependence of the structure of liquid metals with covalent and ionic bonds

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The application of pressure to liquids causes volume reduction and change of interatomic interaction. Especially in liquid metals with covalency in the bands, the interatomic interact ion strongly depends on the volume. In this study we have investigated the effects of pressure on the structure of liquids with covalency and ionicity in the bonds, such as liquid III-V and II-VI compounds.X-ray diffraction for liquid metals has been performed by using synchrotron radiation. From the pressure dependences of the structure factor and pair distribution function of liquids, it is concluded that the local structure of liquid III-V compounds shows different pressure dependence from that of crystals and systematic variation with atomic number and ionicity. With increasing pressure, the local structure of liquid GaSb contracts nonuniformly and its coordination number increases. In liquid InSb which has larger ionicity than that of GaSb, the change in the pressure dependence of the local structure was observed at about 10 GPa from nonuniform to uniform contract ion. The local structure above 10 GPa is different from those of the high pressure crystal l ine phases. In liquid CdTe, a sharp structural transformation was observed around 2 GPa from the zincblende-like to the rocksalt-like local structure. This pressure-induced structural transformation is similar to that in the crystal, in contrast to the different pressure dependence of the liquid structure from that of the crystal in Si, Ge and III-V compounds. This difference should originate from a large ionicity in the bonds in CdTe.