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.

MRCI method with aug-cc-Pvtz,aug-cc-pVQZ,cc-pV5Z,6-311 ++ g(d,p) and 6-311 ++ g(3df,3pd) basis sets is used to calculate potential curves of OH ground state and the first excited state.Murrell-Sorbie potential functions are fitted.Force constants and spectroscopic data are obtained.Our results are in agreement with experimental values.

With relativistic effective cores potential(RECP) for Cu and Te atom,B3LYP method with LANL2DZ basis set is used to optimize structure of CuTe,Cu₂ and Cu₂Te molecules.It shows that the ground state of CuTe and Cu₂ molecules is ²Π and ¹∑_g⁺ respectively and the ground state of Cu₂Te molecule is C_2V symmetry ¹A₁ state.Dissociation energy,harmonic frequency and force constant are calculated.Murrell-Sorbie potential energy functions of CuTe and Cu₂ molecules are fitted by least square fitting.Potential energy function of Cu₂Te ground state is given by many-body expansion theory.Potential surface shows clearly structure of Cu₂Te molecule at ground state.

A New difference scheme, Saulev scheme, is proposed for solving diffusion-convection. equation. Its stability, monotone and Self-adjust are analysed too. Numerical Solutions have been obtained for incompressible viscous flow past a circular cylinder at Reynolds numbers up to 400 with this scheme. Comparing with experiment data and published results, our result is good.