【摘要】 用密度泛函理论为基础的投影缀加波方法、VASP程序包为工具,研究了Ga原子占据1b、2c晶位时六方相和正交相FeMnP_0.67Ga_0.33化合物的相稳定性和力学性质。计算结果表明无论六方还是正交相中Ga原子优先占据2c（对应正交相的8e）晶位,且Ga占2c（或者8e,统称Ga-2c）时体系的能量显著低于Ga占1b的情况,因此Ga原子无序占位的可能性很小。Ga-2c的六方相和正交相均满足热力学稳定条件、力学稳定条件和动力学稳定性条件,并且两相的基态能量非常接近。0K时正交相为基态,计入晶格振动和热电子激发对自由能的贡献后,温度高于215K时六方相更为稳定。Ga-2c六方相具有良好的力学性能,而Ga-2c正交相呈明显的脆性。更多还原

【Abstract】 The phase stability and mechanical properties of hexagonal（hex） and body centered orthorhombic（bco） phases of compound FeMnP_0.67Ga_0.33 were studied when Ga atoms occupy the 1b/2c sites by using the projector augmented wave method implemented in Vienna ab initio simulation package in the framework of density functional theory.The results indicate that Ga atoms prefer to occupy the 2c（8e for bco phase） position in both hex and bco phases of compound FeMnP_0.67Ga_0.33.The total energies of compound FeMnP_0.67Ga_0.33 for Ga atoms occupying the 2c position are significantly lower than that for Ga atoms occupying the 1b position.Therefore,the possibility of disordered occupation of Ga atom is very small.Both hex and bco phases of compound FeMnP_0.67Ga_0.33 with Ga atoms occupying the 2c（8e） position show the thermodynamic,mechanical and dynamic stability conditions of crystals.The ground-state energies of hex and bco phases of compound FeMnP_0.67Ga_0.33 are very close to each other.The bco phase is the ground state at 0 K,but taking into account the lattice vibration and the thermal electron excitation,the hex phase is more stable when the temperature is higher than 215 K.The hex phase of compound FeMnP_0.67Ga_0.33 with Ga atoms occupying 2c position exhibits good mechanical properties,while its bco counterpart is obviously brittle.更多还原