高压下TiC的弹性、电子结构及热力学性质的第一性原理计算

摘要

First-principle investigations of the elastic, electronic and thermodynamic properties of TiC in NaC1 structure under high pressure are conducted by using the plane-wave pseudopotential method and quasi-harmonic Debye model. The obtained lattice parameters, elastic constants and moduli at p = 0 GPa and T = 0 K are in very good agreement with the available experimental data and other theoretical results. According to the analysis of the density of states, the Ti--C bond becomes stronger with pressure increasing. The values of bulk modulus, thermal expansion coefficient, Debye temperature, entropy, Griineisen parameter and heat capacity (Cv) at different pressures and temperatures are obtained successfully by using the quasi-harmonic Debye model. The influence of pressure on bulk modulus, thermal expansion parameter and Debye temperature is greater than that of temperature. The Cv decreases with the increase of pressure under the same temperature and tends to the Dulong-Petit limit at high temperature.%利用基于密度泛函理论的第一性原理平面波赝势方法并结合准谐德拜模型研究了NaCl结构的TiC在高压下的弹性性质、电子结构和热力学性质．计算所得零温零压下的晶格常数、体弹模量及弹性常数与实验值符合得很好．零温下弹性常数和弹性模量随压强增大而增大．通过态密度和电荷密度的分析，Ti—C键随压强增大而增强．运用准谐德拜模型，成功计算了TiC在高温高压下的体弹模量、熵、热膨胀系数、德拜温度、Griineisen参数和比热容．结果表明压强对体弹模量、热膨胀系数和德拜温度的影响大于温度对其的影响．热容随着压强升高而减小，在高温高压下，热容接近Dulong-Petit极限．