In this study, tantalum carbide (TaC) samples were placed in a diamond anvil cell to study the equation of state at room temperature and high pressure using synchrotron radiation X-ray diffraction. By fitting the data at ambient pressure and up to the highest pressure of 38.5[Formula: see text]GPa, we obtained the bulk modulus and first derivative of TaC as [Formula: see text] (6.8) GPa and [Formula: see text] (0.49), respectively. In addition, we calculated the bulk modulus and band structure of TaC under high pressure using density functional theory. The obtained bulk modulus is 267 (3)[Formula: see text]GPa. TaC is metallic in nature throughout the entire pressure range. We studied the high-pressure deviatoric stress of TaC using linewidth analysis method. We found that TaC can support a maximum differential stress of up to 18.6[Formula: see text]GPa at the highest pressure of 38.5[Formula: see text]GPa.

We have studied the high-pressure compression behavior of molybdenum up to 60 GPa by synchrotron radial x-ray diffraction（RXRD） in a diamond anvil cell（DAC）. It is found that all diffraction peaks of molybdenum undergo a split at around 27 GPa, and we believe that a phase transition from a body-centered cubic structure to a rhombohedral structure at room pressure has occurred. The slope of pressure–volume curve shows continuity before and after this phase transition,when fitting the pressure–volume curves of the body-centered cubic structure at low pressure and the rhombohedral structure at high pressure. A bulk modulus of 261.3（2.7） GPa and a first-order derivative of the bulk modulus of 4.15（0.14） are obtained by using the nonhydrostatic compression data at the angle ψ = 54.7°between the diffracting plane normal and stress axis.

The equation of state (EOS) of HfC and nanosized TiC at high pressure has been studied by means of synchrotron radiation X-ray diffraction (XRD) in a diamond anvil cell (DAC) at ambient temperature, and density functional theory (DFT) calculations. XRD analysis showed that the cubic structure of HfC and nanosized TiC maintained to the maximum pressures. The XRD data yield a bulk modulus [Formula: see text] GPa with [Formula: see text] of HfC. In addition, the bulk modulus of nanosized TiC derived from XRD data is [Formula: see text] GPa with [Formula: see text].

The structure and properties of the nanosized [Formula: see text] under high pressure have been investigated by synchrotron X-ray diffraction in the diamond anvil cell combined with the first-principle methods based on density functional theory. The experimental data demonstrate that nanosized [Formula: see text] is highly stable upto 31.3 GPa and bulk modulus is [Formula: see text] GPa. The calculated results by [Formula: see text] indicate that [Formula: see text] undergoes structural transition from cubic fluorite-type structure to orthorhombic [Formula: see text]-[Formula: see text]-type structure at 20 GPa. The indirect band gap [Formula: see text] is 1.89 eV and increases with the increasing pressure while it suddenly reduces to 1.62 eV at transition pressure. The transition pressure calculated by GGA is 40.3 GPa.

室温下,以氦为传压介质的准静水压环境中加压到41GPa,在两柱全景金刚石对顶砧中加压到70GPa,研究了铌在高压下的强度和状态方程.准静水压下,X射线衍射数据拟合得到的体弹模量和其一阶导数分别为166(2)GPa和3.2(2).铌的差应力与剪切模量的比值(t/G)在超过6GPa后几乎为常数,表明由于塑性形变而发生屈服.结合高压下的剪切模量,发现铌在6GPa时由于塑性形变而发生宏观屈服时受到的差应力约为1.26GPa.差应力从2到6GPa可以表示为t=-0.557(94)+0.306(21)p,其中p是压力,单位是GPa.差应力在30GPa后再次增大,表明铌开始出现强化现象,此时对应的差应力约为1.67GPa.在70GPa时,铌受到的差应力最大,且约为3.96GPa.