We performed first-principles calculations of Mn-doped structures in which Mn atoms substitute Ti atoms.Formation energy,density of state and magnetic moment are calculated for Mn ions doped TiO₂(001) and F-TiO₂(001) thin films.In all doping configurations adsorption of F atoms on surface lowers formation energy of TiO₂:Mn system significantly.Magnetic moments of Mn ions are reduced,whereas those of O atoms on surface are increased.Magnetic moment of O atoms is mainly derived from spin polarization p_x and p_y orbitals.F adsorption promotes doping of Mn atoms and improves stability of structure,magnetism,and metallicity to a certain extent.

Simulation of multi-medium compressible flows is generally on structured meshes. As triangular meshes provide a flexible way for decomposing a complex domain, we present an interface treating method for multi-medium flows on triangular meshes with a rGFM (real ghost fluid method). A level set function is used to capture interface. A Riemann problem is constructed at interface to provide fluid states. By defining interface boundary conditions with these states, calculation can be carried out as if in a single medium flow. A high-accuracy RKDG method is then employed to discretizing equations. Several examples are given to test robustness and efficiency of the algorithm. It shows that the method can capture sharp interface and shock wave accurately.

Three-dimensional CFD technology is applied in a RADICL model by solving laminar Navier-Stokes equations and transportation equations to study iodine molecule dissociation rate,iodine atom pumping rate,singlet oxygen yield rate and small signal gain at different flow rate ratio of primary and secondary flow.It is found that an appropriate flow rate ratio plays an important role in spatial distribution of the small signal gain.Rich or poor oxygen conditions go against with a proper gain.

We summarize conservative remapping algorithms based on ENO (essentially non-oscillatory) interpolation. Three numerical techniques in computational fluid dynamics are discussed:overlapping mesh method, adaptive refinement mesh method and moving mesh method. Physical quantities transfer between meshes. Conservativeness is important, especially in computing shock and contact discontinuity. We propose a remapping algorithm based on ENO which is conservative and accurate in transferring physical quantities between meshes and give numerical examples. It shows that the algorithm has ability of resolving conservative problems with above mesh techniques in computational fluid dynamics.

The Level-Set discontinuity tracking technology is extended to the simulation of general compressible multimaterial flows.A Level-Set function is used to keep the track of the interface and discontinuity.A conservative high order accurate WENO scheme is employed.The ghost fluids are constructed in the narrow band region with solution of the Riemann problem.The GFM (ghost fluid method) is implemented for the study of material interface and general discontinuity such as detonation discontinuities.The algorithm is applied to simulate multi-material fluid flows and satisfactory numerical results are obtained.

By predicting the real fluid status rather than the ghost fluid status with a Riemann problem,a simple and efficient extension of the ghost fluid method in multi-dimension is introduced. Riemann problems are constructed at the interface and solved to define boundary conditions of fluid on both sides of the interface.Since the Riemann problem solvers describe fluid state reasonably and the normal velocity and pressure are continuous across the interface,a more accurate interface boundary condition is obtained. Conservation error shows that the method incurs minor errors. Numerical experiments show that this method captures the interface and shock waves correctly.

According to the ENO scheme on structured grids, a class of weighted ENO finite volume scheme on unstructured mesh is developed. On every control volume, it constructs a new weighted quadratic reconstruction polynomial which can save computational costs. It also uses a method which can resolve the overdetermined systems and do not affect the accuracy of the schemes. Besides, the selection of interpolation points and the construction of weight are presented, Third order TVD Runge Kutta time discretization is used. In order to accelerate the convergence, local time step is introduced. The numerical experiments show the scheme effective.