金刚石压砧内单轴应力场对物质状态方程测量的影响

Effect of uniaxial stress field on determination of equation of state in diamond anvil cell

金刚石压砧的几何结构使得在高压下封垫内的样品通常处于单轴应力场中:压砧轴向加载应力最大,径向应力最小.由于金刚石压砧内非静水压单轴应力场的影响,用传统的高压原位X射线衍射方法测得的物质压缩曲线一般位于理想静水压压缩曲线之上.利用金刚石压砧径向X射线衍射技术以及晶格应变理论,结合最近的钨、金刚石和硼六氧样品的高压原位同步辐射径向X射线衍射实验结果,从宏观差应力、样品强度、标压物质和待测物质强度的关系三个方面分析讨论了金刚石压砧内单轴应力场对物质状态方程测量的影响及解决方案.

Samples in a gasketed diamond anvil cell （DAC） are usually subjected to a uniaxial stress at high pressure due to the geometric structure of the DAC, namely a maximum stress along the cell loading axis and a minimum stress in the radial direction.Using conventional DAC in situ high pressure X-ray diffraction method, the measured compression curves often lie above the hydrostatic compression curves because of the effect of uniaxial stress field.Using the technique of DAC radial X-ray diffraction and the lattice strain theory, through the recent experiments with W, diamond and B6O samples,we discussed how the unixalxial stress filed, sample strength, and the sample difference between the sample material and pressure standard material affect the determination of equation of state.