高压下金属间化合物 CaAlSi 的电子结构和晶格动力学性质

摘要

Using first-principles which base on density functional theory,systematacially research on the electronic structure and lattice dynamics of ternary intermetallic compounds CaAlSi under high pressure was conducted.The ternary intermetallic compounds CaAlSi has six angles honeycomb structure similar with MgB2 ,except that Ca atom replaces the position of Mg atom,Al atom and Si atom occupy the position of B atom disorderly.According to calculations on energy band and three-di-mensional Fermi surface,we discover that energy band experiences electron topological changes nearby CaAlSi fermi surface under pressure.The pressure can lead to electronic topology structure phase change.The lattice dynamics of the CaAlSi are studied under pressure.The investigation shows that optical branchs soften along the A-L-H line and phonon modes harden under pressure.It indicates that the structure of the intermetallic compound is unstable under pressure,and a new structure may be found in the case of increasing pressue.%利用基于密度泛函理论的第一性原理方法，研究了三元金属间化合物 CaAlSi 在高压下的电子性质和晶格振动性质。三元金属间化合物 CaAlSi 具有和 MgB2类似的六角蜂巢状结构，Ca 原子取代了 Mg 原子的位置，Al、Si 原子无序地占据 B 原子的位子。通过对 Ca 三元金属间化合物能带和三维费米面的计算，发现在压力的作用下 CaAlSi 费米面附近的能带发生了电子拓扑变化，压强可以导致电子拓扑结构相变（ETTs）。通过晶格动力学的研究发现，在压力的作用下，CaAlSi 的光学支沿着 A-L-H 方向逐渐软化，声学支逐渐变硬。说明此金属间化合物在压力的作用下，其结构不是很稳定，随着压力的继续增大，可能会有新的结构出现。