过渡金属铝化物 FeAl 和 CoAl 弹性性质的第一性原理研究

摘要

本文通过第一性原理计算（密度泛函理论结合均匀形变方法）得到过渡金属铝化物FeAl和CoAl的二阶和三阶弹性常数，这些弹性常数是通过拟合计算出的能量与应力关系得到的．计算结果和理论数据及实验值符合的很好．接下来本文又研究了 FeAl和CoAl在不同压强下的弹性性质．不同压强下的弹性常数 Cij ，体模量 B ，剪切模量 G ，泊松比σ也成功的得到了．B/G比值和柯西压强 PC都表明在零压下FeAl和CoAl表现出脆性．在压强小于60GPa的情况下，增大压强可以增强它们的韧性，但它们始终表现为脆性．%The second-and third-order elastic constants of the B2-type translation-metal aluminides FeAl and CoAl have been calculated by using first-principles calculations based on density functional theory , in combination with the scheme of homogeneous deformation ,they are obtained by fitting the polynomi-als to the calculated energy-strain relationships .The calculated results are in good agreement with the a-vailable theoretical values and experimental data .We have also investigated the elastic properties of FeAl and CoAl under high pressures .The elastic constants Cij ,bulk modulus B ,shear modulus G and Pois-son’s ratio σ,as a function of pressure are presented .Through the Pugh ratio B/G and Cauchy pressure PC under different pressures ,the B2-type translation-metal aluminides FeAl and CoAl are predicted to have brittle behaviors at zero pressure .The pressure could yield improved ductility of FeAl and CoAl without significant changes at P < 60GPa ,but they have brittle behaviors in the pressure range of 0-60GPa .