BaC_2高压相R■m的电子结构与力学性质的第一原理

First-Principles Investigations of Electronic and Elastic Properties of High Pressure-Phase R■m in BaC_2

采用基于密度泛函理论的第一性原理方法研究BaC2高压相R■m的晶体结构、力学、热力学和电子结构等性质.计算结果表明:BaC2的I4mmm相较高压相R■m的离子性更强.在0K时,由BaC2的I4mmm相转变为R■m相的压强为3.6GPa,与实验结果相符.高压相R3m的弹性常数满足波恩-黄昆判据,因而其晶格力学性质稳定.布居数分析表明,在高压下,从Ba原子至C原子的电荷转移在I4mmm至R■m相变过程中所起的作用较大.

The crystal structure, mechanical, thermodynamic, and electronic properties of the high pressure phase R3m in BaC2 were investigaed by means of first-principle method of the density functional theory. The calculation results show that R3m phase is a more ionic semiconductor material, compared with the I4mrnm phase in BaC2. The phase transition pressure from I4mmm to R3m is 3.6 GPa, and agrees with experimental result. The elastic constants of R3rn structure meet the Bonn-Huang Kun criterion, and thus its lattice is dynamics stable. The population analysis shows that the electron transfer from Ba atom to C atom under high pressure plays an important role in the transition from I4mmm to R3m phase in BaC2.