Density Functional Crystal Structure and Electronic Structure Calculations on Co and Ti-Doped CdS

The structure and electronic properties of zinc blende CdS and CdS : M(M= Co,Ti) are studied from DFT based first-principles pseudopotential calculations. It shows that the M doped material have a smaller lattice constant, which results in a local lattice distortion. The charge density is calculated and differences between the pure and doped materials are compared. Results reveal that for the Co doped material,more electrons will be transferred from Co atom to the surrounding S atoms,and the transferred charge finally influences the charge redistribution of the Cd atoms that connected with the S atoms in other directions. For the non-magnetic metal Ti doped cases, the doped Ti atom changed a little the charge distribution around the surrounding S atoms, and charge distribution around the Cd atom is almost the same as the undoped case. The band structure and density of states (DOS) are calculated,which show that CdS : Co is ferromagnetic semiconductor while CdS :Ti is degenerate semiconductor due to the introduction of Co 3d and Ti 4d.