Fe_2TiAl热膨胀和弹性性质的第一性原理研究

First-Principles Study on Thermal Expansion and Elastic Properties of Fe_2TiAl

基于晶格动力学理论,得出了Fe2TiAl的声子谱;考虑到晶格的离散效应,并且将晶体中原子的振动用3n个无相互作用的声子来描述;基于密度泛函理论计算Fe2TiAl的基态能量和力常数矩阵,同时采用声子谱的方法来计算Fe2TiAl的准谐自由能,通过对自由能求极小值获得热平衡体积,并在此基础上获得热膨胀系数、等温体模量和热容;基于弹性理论,研究了Fe2TiAl的弹性性质,并计算了Fe2TiAl的等熵弹性常数和Caushy压强随温度的变化关系,同时讨论了Fe2TiAl的塑性。

Based on the theory of lattice dynamics,the phonon spectrum of Fe2 TiAl is obtained.It takes into consideration of the interaction between atoms in crystal,also the lattice of discrete effect, and the vibration of the atoms in crystal is described by 3n phonon with no interaction.Based on den-sity functional theory,we calculated the ground state energy and force constant matrix of Fe2 TiAl.At the same time,we calculated the quasi harmonic free energy of Fe2 TiAl with the method of phonon spectrum.By means of calculating the minimum of free energy,we obtained the thermal equilibrium volume,and on this basis,the thermal expansion coefficient,isothermal bulk modulus and heat ca-pacity was obtained.Based on the elastic theory,we studied the elastic properties of Fe2 TiAl,and calculated the isentropic elastic constants and Caushy pressure of Fe2 TiAl with the temperature chan-ges.At the same time,we discussed the plasticity of Fe2 TiAl.