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

对液体施加压力会导致体积减小和原子间相互作用的变化。特别是在带内具有共价性的液态金属中，原子间相互作用离子强烈地依赖于体积。在这项研究中，我们研究了压力对具有共价性和离子性的液体结构的影响，如液体III-V和II-VI化合物。用同步辐射对液态金属进行了X射线衍射。从液体的结构因子和对分布函数的压力依赖关系可以看出，液态III-V化合物的局域结构表现出与晶体不同的压力依赖关系，并随原子序数和电离度的系统变化。随着压力的增加，液态GASB的局部结构收缩不均匀，配位数增加。在离子度大于GaSb的液体InSb中，在10 Gpa左右观察到局域结构的压力依赖关系从非均匀收缩离子向均匀收缩离子转变。在10 Gpa以上的局域结构与高压晶体L相的结构不同。在液态CdTe中，在2 Gpa附近观察到了从类闪锌矿到类岩盐局部结构的急剧结构转变。这种压力诱导的结构转变类似于晶体中的结构，而不同于Si、Ge和III-V化合物中晶体的液体结构随压力的变化。这种差异可能源于CdTe中的键具有较大的离子活性。

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.