First-principles Study On Physical Properties Of TM-Si Transition Metal Silicide

Transition metal silicides have become one of the hot materials in condensed matter physics due to their unique physical properties.The research and application of transition metal silicides have always been the focus of attention of numerous experts and scholars,especially related to the application of low temperature ductility and high temperature strength.However,it is worth noting that many transition metal silicides are brittle or semi-brittle at room temperature,which makes their manufacture or processing difficult.In order to further study and apply transition metal silicides,it is necessary to clarify and study the physical properties of transition metal silicides in more detail.So far,the physical properties of Ti-Si and Zr-Si binary transition metal silicides have not been systematically elucidated.In this thesis,the physical properties of Ti-Si and Zr-Si binary transition metal silicides are studied by first-principles calculations,including the structural properties,mechanical properties,anisotropy and electronic properties of the compounds.Doping is a common and effective method to improve the physical properties of materials.In order to improve the inherent brittleness of transition metal silicides and the generation of cracks in the manufacturing process,three different positions of hydrogenation doping models were designed to hydrogenate TM₅Si₄（TM=Ti,Zr,Hf）compounds,and the effects of hydrogenation doping on the physical properties of Ti₅Si₄,Zr₅Si₄ and Hf₅Si₄ compounds were discussed.The results show that Ti-Si and Zr-Si binary transition metal silicides conform to the characteristics of thermodynamic and kinetic stability,and are stable compounds in the ground state.Three Ti-Si compounds and six Zr-Si compounds are brittle.In addition,the formation enthalpy and phonon dispersion curves indicate that the hydrogenated TM₅Si₄（TM=Ti,Zr,Hf）compounds are stable structures.TM₅Si₄ and the H doped models at three different positions showed mechanical stability in the range of elastic deformation.H doping enhanced the shear deformation resistance and hardness of Zr₅Si₄ and Hf₅Si₄,and significantly enhanced the ductility of Ti₅Si₄.The electronic structure shows that TM₅Si₄ and three H-doped compounds have metallic properties.The calculated electronic structure explains that the low elasticity and hardness of H-doped TM₅Si₄ are attributed to the formation of H-TM and H-Si bonds in the TM₅Si₄ silicides.