超高压下碘的结构相变

 采用DAC高压X光技术，在320 GPa压力下，对碘进行了结构相变的研究。用耐腐蚀材料Mo作封垫，在室温和无保护气氛下装样。采用Mo内标和红宝石荧光测量进行压力校准。结果表明，在21 GPa时，开始发生结构相变，由面心正交相（Ⅰ相），转变为体心正交相（Ⅱ相），体积缩小2%左右。在21~25 GPa之间为两相共存区；在25 GPa以上完全转变为新的高压单相（Ⅱ相）。此相变为可逆相变。

THE STRUCTURE PHASE TRANSITION OF IODINE AT HIGH PRESSURE

The structure phase transitions of iodine have been studied by using X-ray diffraction with a diamond anvil cell at high pressure up to 32 GPa. As iodine is reactive with iron in air, a corrosion-resisting and high-strength gasket was put between the diamonds, thus the sample can be mounted at atmospheric pressure and room temperature. Pressure was measured in terms of the ruby fluorescence and the molybdenum diffraction as an internal pressure standard. According to the X-ray diffraction results, iodine undergoes a structural phase transition at 21 GPa from face centre orthorhombic phase to body centre orthorhombic phase. A change of volume is 2%. At 21~25 GPa, the coexistence of two phases has been observed. Above 25 GPa, the single new phase of the high pressure structure appeared. When pressure goes inversely, this transition was found to be reversible.