The uniform electron gas placed between two reservoirs is used as a model system for molecular junctions under an external bias. The energetics of the electron gas are calculated by generalizing the Thomas-Fermi-Dirac (TFD) model to nonequilibrium cases. We show that when the bias voltage is not zero, the first Hohenberg-Kohn (HK) theorem breaks down, and energies of the electron gas can be determined by the total electron density together with the density of nonequilibrium electrons, supporting the dual-mean-field (DMF) theory recently proposed by us [J. Chem. Phys. 139, (2013) 191103]. The generalization of TFD functionals to DMF ones is also discussed.

Influence of the magnetic field on the energy of the spin polarization state of a two-electron system in two-dimensional quantum dots (QDs) is studied by using the method of few-body physics. As example, a numerical calculation is performed for a GaAs semiconductor QD to show the variations of the ground-state energy $E_0,$ the spin-singlet energy $E_1(A)$ and spin-triplet energy $E_1(S)$ of the first excited state and the energy difference (i.e. $\Delta E(A)$ and $\Delta E(S)$) between the first excited and ground states with the effective radius $R_0$ of the QD and the magnetic field $B.$ The results show that $E_0$ increases with increasing $B,$ but decreases with increasing $R_0;$ in the magnetic field, the spin-singlet energy $E_1(A)$ of the first excited state splits into two levels as $E_{1+1}(A)$ and $E_{1-1}(A),$ the spin-triplet energy $E_1(S)$ of the first excited state splits into two sets as $E_{1+1}(S)$ and $E_{1-1}(S),$ and each set consists of three "fine structures" which correspond to $M_S=1,0,-1,$ respectively; each energy level (set, energy difference) decreases with increasing $R_0,$ but there are great differences among the changes of them with $B$: $E_{1+1}(A),$ $E^{M_S}_{1+1}(S),$ $\Delta E_{1+1}(A),$ and $\Delta E^{M_S}_{1+1}(S)$ increase significantly with increasing $B,$ but the variations of $E_{1-1}(A),$ $E^{M_S}_{1-1}(S),$ $\Delta E_{1-1}(A),$ and $\Delta E^{M_S}_{1-1}(S)$ with B are relatively slow; the splitting degree of each energy level (set, energy difference) is proportional to the first power of the magnetic field $B.$

Based on the density functional theory (DFT), the first-principles methods are used to study and compare the electronic structures and optical properties of Mg-, Sr-doped $CaF_2$ systems with those of $CaF_2$ bulk in detail. In contrast to $CaF_2$ bulk, the band gaps of doped systems become narrower and the new peaks of density states appear. The orbital interactions between $Mg,$ $Sr$ atoms and $Ca$ atom are enhanced near the Fermi level, besides, the doped systems all show single dielectric properties and their absorption coefficients for ultraviolet light are reduced greatly, for $Ca_7SrF_{16}$ system, there is a small absorption peak at 25.44 eV. Compared with $CaF_2$ bulk, doped systems have much lower extinction coefficients and much higher light transmittance in the ultraviolet region. In addition, their reflection and loss peaks all display red shift and the peak value reduce.

Applying scaling theory of polyelectrolyte adsorption, and according to ratio of the dielectric constant between the medium and the substrate, and taking into account strong interaction between polyelectrolytes of multivalency adsorption, we proposed a scaling theory of the approximation method on a repulsive charged surface. It is divided into two kind phase diagrams that one is qualitatively different. This shows when the surface charge density is low (or the bulk counterion density is high), the surface and the bulk counterion density are almost the same. Once the surface charge density is high enough, counterions condense on the surface. In this regime, polyelectrolytes of lower valency form a correlated many-chain state. As their valency is high enough, the state turns out to be single-chain because of stronger repulsion between neighboring chains.

Investigate the dissociation and ionization process of cyclopropanone molecules by using the Density functional method. Find the transition states of cyclopropanone molecule and ion, and get the products from transition state to isomer. At the same time, calculate frequency and energy. Confirm their transition states between the reactants and resultants through the Intrinsic Reaction Coordinates (IRC) calculation.

We performed a molecular theory to study the switching mechanism of mixed brushes. For mixed brushes, because of the different solvent selectivity, one species forms the poor solvent layers, whereas another species creates the upper, good solvent layer. The structural properties of the mixed brushes were analyzed in detail for various solvent responds. The thermodynamic properties of the mixed brushes, such as the lateral pressure-area isotherms and chemical potentials, are studied as a function of surface coverage. The possibility of perpendicular segregation in mixed brushes is explained. The presented results allow us to quantify the responsive features of mixed brushes and provide guidance for the design of multicomponent brushes for specific applications.

A molecular beam experiment on the formation of $H^+_3$ has been carried out by using tunable vacuum ultraviolet (VUV) synchrotron radiation. Reflectron time-of-flight mass spectrometer is applied to detect the signal of $H^+_3.$ The ionization energy (IE) of $H_2$ and the appearance energy (AE) of $H^+_3$ are determined to be 15.41 eV and 14.61 eV, respectively, by measurements of photoionization efficiency (PIE) curves. Additionally, two most likely $H^+_3$ formation ways, $(H_2)2\rightarrow H^3_+  +H$ and $(H_2)_3 \rightarrow H^+_3 +H+H_2,$ are discussed by ab initio calculations at CCSD(T) and MP2 level with aug-cc-pVQZ basis set and compared with the experimental result. The optimized geometries of species involved in the dissociative photoionization channels are also determined at MP2/aug-cc-pVQZ level.

We investigate the structure of an Aharonov-Bohm interferometer with a quantum dot coupling to left and right electrodes. By employing cluster expansions, the equations of motion of Green's functions are transformed into the corresponding equation of motion of connected Green's functions, which provides a truncation scheme. With this method under the Lacroix's truncation approximation, we show that Fano resonance causes a decoherence of the Kondo singlet.

The dynamical behavior of two-color ultrashort laser pulse propagating in a molecular medium 4,4'-bis(di-n-butylamino)stilbene (BDBAS) has been studied by employing an iterative predictor-corrector finite-difference time domain (FDTD) technique to solve the Maxwell-Bloch equations. The results indicate that the spectrum of electric field shows oscillation feature around the two-photon resonant frequency when the delay time exists due to the interaction between two sub-pulses. The optical limiting window turns narrower and the saturation value of output intensity gets larger with the presence of delay time compared with no delay time case. The dynamical TPA cross section is smaller with the increase of delay time. The studies suggest a method to modulate the nonlinear optical properties of the medium by controlling the delay time of the two-color pulse.

Electronic states of the $m$-$C_6H_4F^+_2$ ion were studied by using the CASPT2 and CASSCF methods in conjunction with a contracted atomic natural orbital (ANOL) basis set. For the five lowest-lying states, geometries and adiabatic excitation energies $(T_0)$ were calculated at the CASPT2 level. The CASPT2 $T_0$ values and CASPT2 $T'_v$ values are in reasonable agreement with the available experimental data. The assignments of the $B,$ $C,$ and $D$ states of the $m$-$C_6H_4F^+_2$ ion were difficult since the three states are closely lying. Based on the CASPT2 $T_0$ calculations, the $X,$ $A,$ $B,$ $C,$ and $D$ states of the $m$-$C_6H_4F^+_2$ ion were assigned to $1^2A_2,$ $1^2B_1,$ $2^2B_1,$ $1^2A_1,$ and $1^2B_2,$ respectively, which supports the suggested assignment of the lowest excited state to $^2B_1$ by Tsuchiya et al. based on their experiments.

By using two model potentials chosen, the second outermost back rescattered ridges (BRR) of the two-dimensional (2D) momentum spectra of $H^-$ ion in the linear polarization laser fields are studied under the strong-field approximation (SFA). The results show that the polarization potentials in the two model potentials have little effect on the 2D momentum spectra, the number of BRR increases and the fluctuation of angular distributions along the second BRR decreases with the increase of the laser intensity, but the accurate electron-atom elastic scattering cross sections can be retrieved directly along the second outermost BRR by the polynomial fitting method.