Mg-Nd合金中金属间化合物稳定性的第一性原理研究(英文)

First-Principles Study on the Stabilities of the Intermetallic Compounds in Mg-Nd Alloys

采用基于密度泛函理论的第一性原理赝势平面波方法,对Mg-Nd二元合金中各种金属间化合物进行了结构优化,得到了其基态能量,并从合金形成热和结合能两方面研究了这些金属间化合物的结构稳定性。结果表明:各金属间化合物结合能的绝对值随Nd含量的增加而升高,其中MgNd结合能的绝对值最大,而Mg12Nd结合能的绝对值最小。这表明在Mg-Nd形成的金属间化合物中,MgNd的结构最为稳定,而Mg12Nd的稳定性最差。这一结果与实验数据相一致,在Mg-Nd合金相图中并没有出现Mg12Nd相。另外,还对这些结构的电子态密度进行了计算,从电子结构的角度对这一结论进行了解释。

Using the first-principle pseudopotential plane wave （PPW） method based on the density functional theory, structural optimization was conducted on various intermetallic compounds of the binary Mg-Nd alloy. With their ground-state energies obtained, the structural stabilities of these intermetallic compounds were studied in terms of formation heat and binding energy of the alloy. The results show that the absolute values of the binding energies of various intermetallic compounds increase with the increase of Nd content, among which the absolute value of the binding energy of MgNd is the greatest while that of Mg12Nd is the smallest. It is indicated that among all the intermetallic compounds formed in Mg-Nd, the structure of MgNd is the most stable while that of Mg12Nd is the most unstable. This result is consistent with the experiment data. The Mg12Nd phase does not exist in the phase diagram of Mg-Nd alloy. In addition, the densities of electronic state of these structures were calculated and an explanation was given in terms of the electronic structure.