Electronic Structure And Physical Properties Of Heusler Alloys Containing Heavy Elements

The materials with special electronic structure can exhibit many novel functions. Thisdissertation is mainly to explore new functional materials with special electronic structurein Heusler alloy containing heavy metal elements. We focus on the Heulser-type Mn3Z,Rh3Z and LaPtBi compounds. Using first principles calculations, we investigated theelectronic structure、magnetic properties and structural stability. A series of significantresults are achieved.The electronic structure and magnetic properties are studies for Heulser-type Rh3Z(Z=Al、Ga、In、Si、Ge、Sn、Pb、Sb) compounds. It was found that the Rh3Z (Si、Ge、Sn、Pb) are half-metallic and the half-metallicity can be kept in a quite wide latticeparameter. This is the first to report the half-metallic materials composed of4d transitionmetal elements and main group elements. Rh3Z (Si、Ge、Sn、Pb) compounds have amagnetic moment of3μB, which follows a rule Mt=Zt-28but not the conventionalSlater-Pualing rule (Mt=Zt-24). Rh3Z (Al、Ga、In、Sb) show a ordinary metallicity.The investigations on the structural stability of Heusler-type Mn3Z (Z=Al、Ga、In、Tl、Si、Ge、Sn、Pb) compounds show that Mn3Z (Z=Ga、In、Tl、Sn、Pb) compounds arestatble in tetragonal phase, which implies that a martensitic transformation is possible tooccur in these compounds. Mn3Z (Z=Al、Si、Ge) is stable in cubic phase. The structuralstability is sensitive to the interatomic space for Mn3Z compounds. The stability willexchange between the cubic and tetragonal phase if the the interatomic space is properlyadjusted. In the transformation process from cubit to tetragonal phase, the magneticmoment of Mn (B) is hardly changed and those of Mn (A, C) show three different changingtendency with the joint effect of p-d and d-d hybridizaiton.The electronic structures in different lattice parameters are studies for Heuslercompound LaPtBi. It was found the band inversion strength decreases with the thedecreasing lattice parameter under the hydrostatic pressure. Both the uniaxial stretch andcompression can increase the band inversion strength. SOC can increase the band inversionstrength and make the toplogical insulativity more stable.