高压下AuCu3热动力学性质的第一性原理研究

利用平面波赝势密度泛函理论研究了AuCu3的结构性质,得到了晶格常数a、体弹模量B0、体弹模量对压强的一阶导数B'0,计算结果与实验值相吻合.通过准谐德拜模型成功地获得了高温高压下Au-Cu3的状态方程、热膨胀系数、热容及德拜温度.     

金红石结构TiO2结构和热力学性质的第一性原理研究

利用基于密度泛函理论的第一性原理计算方法以及准谐德拜模型研究了金红石TiO2的结构和热力学性质。常温常压下所计算的晶格常数、体弹模量及其对压强的一阶导数与实验值和其他理论计算结果相符的较好。另外,我们还计算了体弹模量、热膨胀系数、热容与温度和压强的关系。     

金红石结构TiO2结构和热力学性质的第一性原理研究

利用基于密度泛函理论的第一性原理计算方法以及准谐德拜模型研究了金红石TiO₂的结构和热力学性质.常温常压下所计算的晶格常数、体弹模量及其对压强的一阶导数与实验值和其他理论计算结果相符的较好.另外,我们还计算了体弹模量、热膨胀系数、热容与温度和压强的关系.     

萤石结构TiO2热力学性质的第一性原理计算

利用第一性原理平面波赝势密度泛函理论研究TiO₂的结构,其零温零压下的晶格常数和常温下的体弹模量及其对压强的一阶导数的计算结果与实验值和其他理论计算结果相符.通过准谐德拜模型,获得了相对晶格常数、相对体积、体弹模量、热膨胀系数、热容与温度和压强的关系.     

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

利用基于密度泛函理论的第一性原理平面波赝势方法 并结合准谐徳拜模型研究了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、徳拜温度、 Grüneisen参数和比热容. 结果表明压强对体弹模量、热膨胀系数和徳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.     

常压下固态KNO2热力学性质的密度泛函理论研究

采用密度泛函理论结合准谐德拜模型研究常压下300~725 K间KNO₂立方结构的热力学性质,重点分析常压下定压热容、定容热容、熵、德拜温度、体膨胀系数、平衡体积和体弹模量随温度的变化.结果显示,常压下计算的定压热容随温度的变化与实验数据符合较好,而计算的熵与实验数据相差较大.计算得到KNO₂的平均体膨胀系数约为1.837 8×10^-5K^-1,常温下(300 K)KNO₂的德拜温度约为667.13K.     

MgCNi3超导体在静水压下的弹性性质

 在0.1 MPa到0.5 GPa压力范围内，采用脉冲回波重合法（Pulse-Echo Overlap Method）测量了MgCNi₃超导体的横波及纵波声速，计算了体弹模量B、剪切模量G等弹性参数以及德拜温度、比热等热力学参数随压力的变化。常压下的θ_D与c_V的值分别为454.82 K和111.30 J/(mol·K)。对B-p曲线作线性拟合，得到体弹模量B₀在零压附近的导数B′₀，由此建立了MgCNi₃的状态方程。     

高压下硫化钙的弹性和热力学性质的第一性原理计算

利用基于密度泛函理论的第一性原理平面波赝势方法结合准谐德拜模型研究NaCl结构的CaS在高压下的弹性和热力学性质.计算得到的零温零压下的晶格常数、体弹模量与实验值符合得很好.弹性常数和弹性模量随着压强的增大而增大.压强对体弹模量和热膨胀系数的影响大于温度的影响.热容随压强的升高而降低,在高温下热容接近于Dulong-Petit极限.通过求解Gibbs自由能计算得到B1结构和B2结构CaS的相变压为36.61 GPa.     

铜钨合金高温高压性质的第一性原理研究

采用基于密度泛函理论的第一性原理方法,研究了三种不同比例铜钨合金(Cu3W,Cu W,Cu W3)的基态及高温、高压下的电子结构、弹性性质和热力学性质.弹性常数计算结果表明Cu3W为结构不稳定相,Cu W和Cu W3为结构稳定相,与声子色散曲线得到的结论一致.通过对态密度的分析,发现随压强的增大,金属键键能增大,并且态密度有向深能级移动的趋势.通过准简谐德拜模型和准简谐近似模型分别计算、分析和对比了三种铜钨合金在不同温度和压强下的体弹模量、热膨胀系数、德拜温度和比热容.     

LiH的热力学性质及分子内部运动对体系热力学性质的影响

利用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了LiH在零温零压下的晶格常数、体弹模量,计算结果与实验值和其他理论计算值符合得较好.通过准谐德拜模型计算了LiH在压强为0-80GPa、温度为0-2000K范围内,体积膨胀率、热涨系数、德拜温度及定容热容随压强和温度的变化关系.最后,以代数方法（AM）和势能变分法(PVM)为基础,运用统计热力学理论计算了LiH分子内部运动对体系热力学性质的影响.     

The stabilities, electronic structures and elastic properties of Rb-As systems

The structural, electronic and elastic properties of Rb–As systems (RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3 As in Na3As, Cu3 P and Li3Bi structures, and Rb5 As4 in the A5B4 structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan’s equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young’s modulus, the shear modulus, Poisson’s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.     

First-Principles Calculations of Elastic Properties of LaNi5 Compound

The equilibrium lattice constants, temperature dependence of bulk modulus, the pressure dependence of the normalized volume V/V0, elastic constants Cij and bulk modulus of LaNi5 crystal are obtained using the firstprincipies piane-wave pseudopotential method in the GGA-PBE generalized gradient approximation as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus and temperature up to 2000 K and obtain the relationship between bulk modulus B and pressure at diFFerent temperatures. It is found that the bulk modulus B increases monotonously with increasing pressure. Moreover, the pressure dependences of Debye temperatures and the pressure derivatives of lattice constants are also successfully obtained. The calculated results are in agreement with the experimental data and the other theoretical results.     

First-principles calculations of elasticity and thermodynamic properties of LaNi5 crystal under pressure

This paper investigates the equilibrium lattice parameters, heat capacity, thermal expansion coefficient, bulk modulus and its pressure derivative of LaNi 5 crystal by using the first-principles plane-wave pseudopotential method in the GGA-PBE generalized gradient approximation as well as the quasi-harmonic Debye model. The dependences of bulk modulus on temperature and on pressure are investigated. For the first time it analyses the relationships between bulk modulus B and temperature T up to 1000 K, the relationship between bulk modulus B and pressure at different temperatures are worked out. The pressure dependences of heat capacity C v and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperatures of LaNi 5 at different pressures are successfully obtained. The calculated results are in excellent agreement with the experimental data.     

First-principles calculation of elastic and thermodynamic properties of Ni2MnGa Heusler alloy

The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni 2 MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential (PW-PP) method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus B and temperature T up to 800 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure and decreases with increasing temperature. The pressure dependence of heat capacity C v and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperature of Ni 2 MnGa is determined from the non-equilibrium Gibbs function. Our calculated results are in excellent agreement with the experimental data.     

Theoretical Study of Compressibility and Thermoelasticity of LaNi5-xAlx （x= 0.3, 0.5 and 1.0）

The compressibility, the temperature dependence of bulk modulus, the pressure dependence of normalized volume V/V0, thermal expansion coefficient and Debye temperature of LaNi5-xAlx compounds are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） method, the EOSFIT6.0 software and the quasiharmonic Debye model. The rapid decrease of relative lattice constant a/a0 shows that the deformation is easier in directions normal to the c-axis than that along it. The relationships between bulk modulus B and pressure at different temperatures are also analysed. It is found that the bulk modulus B increases monotonically with increasing pressure. Moreover, the pressure dependences of thermal expansion and Debye temperature are also successfully obtained. The calculated results are in agreement with the experimental data.     

First-Principles Calculations of Elastic Properties of Cubic Ni2MnGa

Dependence of bulk modulus on both pressure and temperature, the elastic constants Cij and the pressure and temperature dependence of normalized volume V/Vo of cubic Ni2MnGa alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus and temperature up to 800 K and obtain the relationships between bulk modulus B and pressures at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure. Moreover, the temperature dependences of the Debye temperature are also analysed. The calculated results are in agreement with the available experimental data and the previous theoreticM results.     

First-principles investigation on the structural and elastic properties of cubic-Fe_2 TiAl under high pressures

The structural, elastic, and thermodynamic properties of cubic-Fe 2 TiAl under high temperatures and pressures are investigated by performing ab initio calculation and using the quasi-harmonic Debye model. Some ground state properties such as lattice constant, bulk modulus, pressure derivative of the bulk modulus, and elastic constants are in good agreement with the available experimental results and theoretical data. The thermodynamic properties of Fe 2 TiAl such as thermal expansion coefficient, Debye temperature, and heat capacity in ranges of 0 K-1200 K and 0 GPa-250 GPa are also obtained. The calculation results indicate that the heat capacities at different pressures all increase with temperature increasing and are close to the Dulong-Petit limit at higher temperatures, Debye temperature decreases with temperature increasing, and increases with pressure rising. The cubic-Fe 2 TiAl is stable mechanically under 250 GPa. Moreover, under lower pressure, thermal expansion coefficient rises rapidly with temperature increasing, and the increasing rate becomes slow at higher pressure.