First principles studies on the electronic structures of LiMxFe1-xPO4 （M = Co, Ni and Rh）

The local crystal structures and electronic structures of LiMxFe1-xPO4 （M = Co, Ni, Rh） are studied through first-principles calculations. The lattice constants and unit cell volumes are smaller for the Co and Ni doped materials than for pure LiFePO4, while larger than for the Rh doped material. The local structures around M atoms in the doped materials are studied in details. The total density of states （DOS） and atomic projected DOS （PDOS） are all calculated and analysed in detail. The results give a reasonable prediction to the improvement of electronic conductivity through Fe-site doping in LiFePO4 material.     

Structural,mechanical, electronic properties,and Debye temperature of quaternary carbide Ti3NiAl2C ceramics under high pressure: A first-principles study

Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye temperature.Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–C.However,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds form.When the pressure reaches 20 GPa,the covalent bonds change to metallic bonds.The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at most.Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics.At 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ductility.However,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure.In addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.