中文摘要：

基于密度泛函理论平面波赝势法的第一性原理计算，研究了过渡金属锇在高压下的状态方程、弹性常数和其它力学性质。计算结果表明：过渡金属锇具有很高的体积模量B0（423．9GPa）和弹性常数C11（771．3GPa）与C33（852．0GPa），与金刚石的（B0=452．8GPa，C11=C33=1082．9GPa）比较，具有超低压缩特性；表征材料抵抗剪切变形能力的弹性常数G44（269．8GPa）和切变模量（276．8GPa）只有金刚石的（C44=586．9GPa，G=537．5GPa）一半，而所成的又是纯金属键，因此锇不具有超硬性。最后，定性分析了它的高体积模量和低硬度的微观电子机制，这对于设计与合成新的超硬性材料具有启发意义。

英文摘要：

The equation of states, elastic constants and other mechanical properties of transition-metal osmium under high-pressure are studied by the first-principles plane-wave pseudopotential calculations based on the density functional theory （DFT）. The calculated results indicate that osmium has high bulk modulus B0 （423.9 GPa） and large elastic constants C1l （771.3 GPa）and C33 （852.0 GPa）compara- ble to diamond （B0 = 452.8 GPa, C11 = C33 = 1 082. 9 GPa）, so it is an ultralow-compressible material. However,its elastic constant C44 （269.8 GPa） and shear modulus G（276.8 GPa）, which indirectly measure hardness,are half of those of diamond （C44 =586.9 GPa,G=537.5 GPa）. Because of its pure metallic bonds,it may not be superhard material. The microscopic mechanism of high bulk modulus and low hardness can be understood from the analysis for electronic structures,and it helps to design and synthesize new superhard material.