Phase transitions of sulfur under high-pressure and high-temperature condition

采用多砧式高压装置MAX80和同步辐射相结合的方法，直接观测了硫磺的高温高压行为。通过使用烧结的金刚石顶锤，将可观测的压力和温度范围扩大到17 Gpa和900℃。在该范围内发现了三个高压相。所有高压相在环境条件下都是不能熄灭的。通过X射线粉末衍射图确定了高压相的晶体结构。高压相1具有六方晶胞，硫原子在其中形成螺旋链。高压相2具有另一个六方晶胞，其结构是由S_6的环状分子构成。高压相3在四方晶胞中含有另一个螺旋链。在室温条件下，观察了所有高压相和低压相的压缩行为。在高压相2的情况下发现了各向异性的压缩行为。在现场观测的基础上，确定了硫的压力和温度相图。

High-pressure and high-temperature behavior of sulfur was directly observed, using a combination of multi-anvil type high-pressure apparatus"MAX80"and synchrotron radiation. Observable pressure and temperature range was expanded up to 17 GPa and 900℃ by using sintered diamond anvils. Three high-pressure phases were found in the range. All high-pressure phases were unquenchable at ambient condition. Crystal structures of the high-pressure phases were determined from their X-ray powder diffraction patterns. The high-pressure phase 1 has a hexagonal cell, in which sulfur atoms form helical chains. The high-pressure phase 2 has another hexagonal cell and the structure is built up of cyclic molecule of S_6. The high-pressure phase 3 contains another helical chains in a tetragonal cell. Compression behaviors of all high-pressure phases and the low-pressure phase were observed at room temperature condition. An anisotropic compression behavior was found in the case of the high-pressure phase 2. The pressure and temperature phase diagram of sulfur was also determined, based on the in-situ observations.