The Electronic Properties Of MAlSi (M=Ca, Sr, Ba) At Different Pressure By First-Principles

Pressure is one of the basic parameters (Pressure, Temperature, Chemical component) which can change the properties of material. High-pressure induces structural phase transitions and electronic transformation of materials, many strange phenomena and properties which is not shown under ordinary pressure will be found under high-pressure. This would have deepened our understanding of the world on substance. The discovery of superconductivity of MgB2 reported in NATURE in 2001 has extensively stimulated worldwide attentions in the scientific field. The superconducting transition temperature of MgB2 reaches about 39 K. By far, this is the highest superconducting temperature in the simple metal compounds. Therefore, the study on the structure and properties of binary, ternary intermetallic with quasi-MgB2 structure in high-pressure has been a focus.The electronic properties and lattice vibration properties of MAISi (M= Ca, Sr, Ba) ternary intermetallic were studied by using First-principles based on the density functional theory under high-pressure. They have similar hexangular honeycomb structure to MgB2, which M (M= Ca, Sr, Ba) atoms substitute Mg atoms, Al and Si atoms randomly occupy B atomic positions. Electronic topological change was found under pressures for CaAlSi and SrAlSi by means of energy band and 3D fermi, while not observed for BaAlSi, in other words, pressure induced Electronic topological transitions (ETTs). The lattice dynamics of the CaAlSi and SrAlSi were studied under pressure. The investigation showed that optical branches softened along the A-L-H line and phonon modes hardened under pressure. It is indicated that the structure of the intermetallic compound was unstable with pressure, and a new structure might be found in case of increasing pressure.