The first principles calculations were performed to investigate site preferences of the alloying elements M (Ti, Nb) doping in Ni3Al, elastic properties and the electronic structure of Ni3Al and Ni3Al-M with the Cambridge sequential total energy package (CASTEP). It was found that M were preferred to replace the Al sites. As the M doping. The bulk, shear and Young's modulus increased and the bulk/shear modulus ratios (B/G) decreased in Ni3Al polycrystalline alloy. While B/G of all alloys were larger than 1.75, signifying that Ni3Al, Ni24Al7Nb and Ni24Al7Ti polycrystalline alloys possessed ductility. Analyzing the electronic structure of Ni3Al and Ni3Al-M, the results showed that the main interaction between the Ni atoms and the Al atoms was covalence in the Ni3Al, after doping elements M (Ti, Nb) in Ni3Al, there was strong orbital hybridization between the Al-3p orbital, Ni-3d orbital and M-d (Ti-3d, Nb-4d) orbital, the covalent bonds between alloying atoms M (Ti, Nb) and their neighbor atoms Ni were stronger than that between Al atom and Ni atom.

The effect of Si concentration on the electronic and optical properties of Si incorporated SnO2 was investigated by density functional theory. SnO2 maintained the direct bandgap after Si incorporation, and the value of bandgap enlarged as the Si concentration increased. The formation of the Si–O covalent bond could reduce electron losses of Sn atoms that resulted in the decrease of electron concentration of SnO2 through the density of states and charge density analysis. On the basis of the calculation results of the optical properties including the dielectric function, refractive index, reflectivity, absorption, and electron energy-loss spectrum, the values of these parameters were reduced at a low energy region and these curves gradually shifted toward high energy as the Si concentration increased. It suggested that the optical properties of SnO2 could be improved by the Si atom over the infrared and visible spectra.