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基于密度泛函理论及密度泛函微扰理论为基础的第一性原理计算,采用虚晶近似的方法,研究了具有hcp结构且Zn含量在2%(原子分数)范围内的8种Mg_(1-x)Zn_x合金的晶格常数、弹性性质和热力学性质。通过优化结构计算Mg和Zn含量不同的Mg_(1-x)Zn_x合金弹性常数,对Young’s模量、Poisson比、弹性各向异性等进行了详细分析,给出了Mg及Mg_(1-x)Zn_x合金的晶格振动Helmholtz自由能、内能、熵和定容热容等随温度变化情况。结果表明,随着Zn含量增加晶格常数a和c均相应减小,弹性常数、自由能和内能增大,熵及定容热容减小;另一方面,随温度升高,Zn含量对自由能和熵的影响程度增大,而对定容热容的影响程度先增大后减小。Mg_(1-x)Zn_x合金中Zn含量的增加有利于提高材料硬度和韧性,但也增大了材料的各向异性。
Based on the first principles calculations based on density functional theory and density functional perturbation theory, eight kinds of Mg_ (2 +) with hcp structure and Zn content of 2% (atomic fraction) 1-x) Zn_x alloys. The Young’s modulus, Poisson’s ratio, elastic anisotropy and so on were analyzed in detail by optimizing the structure elastic constants of Mg_ (1-x) Zn_x alloys with different Mg and Zn contents. Mg, Mg_ (1-x) Zn_x alloy lattice vibration Helmholtz free energy, internal energy, entropy and constant volume heat capacity and other changes with temperature. The results show that with the increase of Zn content, the lattice constants a and c decrease, the elastic constants, free energies and internal energy increase, and the entropy and heat capacity decrease. On the other hand, with the increase of Zn content The degree of influence on free energy and entropy increases, but the degree of influence on constant heat capacity first increases and then decreases. The increase of Zn content in Mg_ (1-x) Zn_x alloy can improve the hardness and toughness of the material, but also increase the anisotropy of the material.