Mg_3Ce基态结构的GGA和GGA+U对比研究

GGA and GGA+U Comparative Study of Ground State of Mg_3Ce

采用基于第一性原理的计算软件VASP对Mg3Ce的基态结构分别在GGA方法和GGA+U方法下进行了研究.通过GGA计算得到的结构常数与实验值吻合,但是计算结果表明基态结构为铁磁结构,而且所得到的磁矩为0.94μB,这些都与实验值不符合.为了更好地描述Mg3Ce的性质,我们引入了GGA+U计算,结果表明当Ueff=7.0eV的时候所得到的结构常数、基态结构和磁矩都与实验值很好地符合,因此引入GGA+U计算是必要的,且Ueff=7.0eV在GGA+U计算中是合理的.通过电子结构,进一步揭示了Mg3Ce的内在机制.发现Ce的f态电子对总的态密度的贡献是很大的,因此对于Mg3Ce性能的研究必须要考虑到f态电子的贡献.

The ground state structure of Mg3 Ce was studied using both GGA and GGA＋U methods within Vienna initio Simulation Package （VASP） based on First-principhs computations. When the U-eff = 7.0 eV the GGA＋U method correctly predicts antiferromagnetic phase as the ground state, and the ob- tained structural parameters and magnetic moment are in good agreement with experimental data, while the GGA method cannot. The electronic structure is calculated for studying the inherent mechanism. From the density of states, it was found that the dominant contribution mainly comes from Ce 4f and 5d states, so the GGA＋U calculation is necessary.