【摘要】 基于密度泛函理论的第一性原理方法,系统研究了三元金属间化合物SrAlSi在高压下的电子性质和晶格动力学性质.三元金属间化合物SrAlSi具有和MgB2类似的六角蜂巢状结构,Sr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SrAlSi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SrAlSi费米面附近的能带发生电子拓扑变化,压力可以导致电子拓扑结构相变(ETTs).通过晶格动力学研究发现,在压力的作用下,SrAlSi的光学支沿着A-L-H方向逐渐软化,声学支逐渐变硬,说明金属间化合物SrAlSi在压力作用下结构不是很稳定,随着压力的继续增大,会有新的结构出现.更多还原

【Abstract】 Electronic and lattice dynamic properties of ternary intermetallic SrAlSi are studied with first-principles calculations based on density functional theory under high pressures. SrAlSi has a similar hexagon-honeycombed structure to MgB2,where Sr atoms substitute Mg atoms,Al and Si atoms randomly occupy the positions of B atoms. It is found that under high pressure electronic topological transition( ETT) occur in the band of SrAlSi near Fermi surface. Lattice dynamics of SrAlSi are studied by phonon dispersion spectra at different pressures. The calculation shows that optical branches soften along A-L-H line and phonon modes harden with increase of pressure. It is indicated that structure of intermetallic compound SrAlSi is unstable under high pressures.更多还原