Multiple exciton generation (MEG) of Si₆X(X=Cu, Ag and Au) clusters is investigated by using symmetry adapted cluster theory with configuration interaction and pseudo potential LANL2DZ basis set. Before MEG calculations, geometrical structures of clusters are optimized and their energy stabilities are confirmed by frequency analysis based on density functional theory method and all-electron double zeta valence quality plus polarization functions primary basis sets DZP-DKH. It indicates that double exciton is found dominating component and MEG of clusters appear in visible range although the strong part is in ultraviolet light range, which provides information for potential materials utilizing MEG to harvest energy of solar light.

A scheme of convolutional perfectly matched layer (CPML) absorbing boundary condition (ABC) is proposed, which is used to truncate finite-difference time-domain (FDTD) method modeling transient electromagnetic (TEM) response. It derives specially CPML formulation dealing explicitly with divergence of magnetic induction and conceives an algorithm calculating convolutional term of z component. Then, the scheme is validated by numerical modeling of a homogeneous half-space model. The results indicate that efficient calculation of TEM is achieved.

In distributed parameter contact algorithm on three-dimensional contact surface,a method for smoothing three-dimensional contact surface is developed. In the method,a smooth contact surface is interpolated with bi-cubic parametric patches. A bi-cubic parametric patch is defined by using local information such as coordinates and normals of vertexes of patch. The smoothing technique provides an accurate representation of actual contact surface which is C¹ continuous in patches and G¹continuous(tangent plane continuous) between adjacent patches. Then C¹ continuous smooth fields of normal pressure and density on smoothed surface are interpolated. And contact points on smoothed contact surface are calculated with Newton-Raphson iteration. Finally,contact constraints are computed with distributed parameter contact algorithm. Numerical examples demonstrate that smoothed contact surface alleviates‘chatter’of nodes and improves convergence behavior.

Based on a mathematical model of non-Darcy unsteady seepage flows in low-permeability porous media with moving boundary conditions,a differential equation of propagation velocity for moving boundary was deduced.It indicates that propagation velocity of a moving boundary is proportional to the second derivative of formation pressure with respect to radial distance on the moving boundary.And with Lagrange three-point interpolation formula,finite difference scheme of governing equation near a moving boundary was obtained.Exact position of a moving boundary is able to be tracked.Numerical results show that the front tracking method describes propagation behaviors of moving boundary of non.Darcy unsteady seepage flows in low-permeability porous media well.

Du Fort-Frankel differential format for mode calculation of unstable resonator is presented.A fast finite differential method based on matrix motion and coordinate system transformation is used to calculate output field of a bare cavity and an active cavity.Calculated results are compared with references.It shows that the method is good both in precision and speed in calculating modes of an active unstable resonator with large Fresnel numbers.It can be 20 to 40 times faster compared with a conventional method.With this method,output power of a HF chemical laser is calculated.It shows that the output power increase with decrease of distance between gain medium and concave mirror.This result is valuable to the design of high power DF chemical laser.

A boundary element method (BEM) based on multiple reciprocity method(MRM) is employed to solve eigenvalue and eigenfrequency of a two-dimensional linear acoustic cavity.By direct searching of the zero-points of determination of a matrix,we determine eigenfrequency of the system.An effective estimation for the first wave-number was suggested based on the principle of wave propagation.Estimation efficiency of several models is calculated.We evaluated fundamental solution's order and found that more than seven reciprocity are needed.Numerical results agree well with analysis and other literature.Estimation for the first wave-number is effective and correct.

An artificial viscosity is presented for Lagrangian hydrodynamics method.The formulation is based on artificial viscosity first presented by Lew.It contains a limiter switching off viscosity for shockless compression.The artificial viscosity reduces dependence of solution on relation of grid to flow structure.The eigenvalue viscosity limiter controls magnitude of the artificial viscosity.By the limiter it is able to distinguish between adiabatic compression and shock compression.The formulation is applicable to any dimensions and to logically rectangular or unstructured grids.

A deconvolution method for electron energy loss spectrum of diatomic molecules is proposed.Fitted energy positions are locked on accurate spectroscopic data.Calculated Franck-Condon factors are adjusted by a quadratic function.Precision requirement for Franck-Condon factors is reduced.Undermined parameters in deconvolution procedure are reduced dramatically.Precision of fitted results is improved. Optimized algorithm in fitting procedure avoids a lot of integral calculations.The program is used to deconvolve electron energy loss spectrum of H_2.Vibrationally resolved optical oscillator strengths are determined.The results agree well with previous experimental and theoretical studies.

The steady uniform shear flow in a low concentration fluidized gas solid granular flow is studied on the basis of the kinetic theory of granular flow and a modified BGK model equation. Explicit expressions of the pressure tensor are obtained as a function of the restitution coefficient. The computation shows the different normal stresses distribution. The results agree well with the Jenkins Richman theories, although significant discrepancy appears for granular temperature distributions.

An imitative calculation on W/C,Mo/Si artificial multilayered films,have been made.The influences of total period numbers and deviation of period thickness on X-ray diffraction peak were given. Two difference deviations, random fluctuation and system linear deviation have been imitated, their influences on X-ray energy distinguish power have been compared.