Electronic Structure and Lattice Dynamics of Intermetallic Compounds CaAlSi at High-Pressure
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摘要: 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。Abstract: 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-dimensional 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.
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图 3 不同压力下CaAlSi的能带结构图
Figure 3. Energy band structures of CaAlSi at different pressures
图 4 CaAlSi在0、3和5 GPa时Г点的能带放大图
Figure 4. Г point the band enlargement map at 0, 3, 5 GPa
图 5 不同压力下的CaAlSi的三维费米面图
Figure 5. CaAlSi three-demensional Fermi maps at different pressures
图 6 CaAlSi在布里渊区Г点处的能带与费米面处的能量差随压强变化关系
Figure 6. CaAlSi in the Brillouin zone Г point of the band and at the Fermi energy difference with the change of pressure
表 1 不同压力下CaAlSi晶格常数
Table 1. CaAlSi lattice constant at different pressures
p/(GPa) a/(nm) c/(nm) 0 0.420 8 0.437 1 3 0.416 4 0.423 6 5 0.414 0 0.415 9 
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