Binding energy, electronic structure and optical properties of pure AlN and Ag, S codoping AlN were calculated with first-principles ultrasoft pseudopotential approach of plane wave based upon density functional theory.It shows that concentration of doping Ag atoms can be increased in AlN and acceptor level becomes shallower by introduction of S atoms. Acceptor Ag atoms play an important role in activating. So Ag, S codoping AlN is expected as an efficient means of p-type doping.Imaginary part of dielectric function and optical absorption spectrum of the doping system show a new peak in low energy region.And absorption edge extends to low energy. Doping system enhances low frequency electromagnetic wave absorption.

Thermodynamic properties of cubic CeO₂ with pressures up 30 GPa and temperatures up to 2 000 K are studied with first principles combined with a quasi-harmonic Debye model,including temperature dependence of equilibrium volumes,bulk modulus,heat capacity and entropy under ambient pressures.Heat capacity,entropy,Debye temperature and volume thermal expansion coefficient under different pressures are successfully obtained.Calculated heat capacity and entropy are in good agreement with experiments under ambient pressure.