Using first-principles calculations within density functional theory, we study the atomic structures and electronic properties of the perfect and defective(2VCu+ InCu) CuInGaSe2/CdS interfaces theoretically, especially the interface states.We find that the local lattice structure of(2VCu+ InCu) interface is somewhat disorganized. By analyzing the local density of states projected on several atomic layers of the two interfaces models, we find that for the(2VCu+ InCu) interface the interface states near the Fermi level in CuInGaSe2and CdS band gap regions are mainly composed of interfacial Se-4p,Cu-3d and S-3p orbitals, while for the perfect interface there are no clear interface states in the CuInGaSe2region but only some interface states which are mainly composed of S-3p orbitals in the valance band of CdS region.
Classical atomistic simulations based on the lattice dynamics theory and the Born core-shell model are performed to systematically study the crystal structure and thermal properties of high-k Hf1-xSixO2 . The coefficients of thermal expansion, specific heat, Grneisen parameters, phonon densities of states and Debye temperatures are calculated at different temperatures and for different Si-doping concentrations. With the increase of the Si-doping concentration, the lattice constant decreases. At the same time, both the coefficient of thermal expansion and the specific heat at a constant volume of Hf1-xSixO2 also decreases. The Grneisen parameter is about 0.95 at temperatures less than 100 K. Compared with Si-doped HfO2 , pure HfO2 has a higher Debye temperature when the temperature is less than 25 K, while it has lower Debye temperature when the temperature is higher than 50 K. Some simulation results fit well with the experimental data. We expect that our results will be helpful for understanding the local lattice structure and thermal properties of Hf1-xSixO2 .
