Structural, vibrational and electronic properties of the zirconium oxide clusters [n=1-6] are calculated to investigate the changes in, lower and higher state by Density functional theory with the B3LYP exchange-correlation functional using LANL2DZ as the basis set. We optimize several isomers for each size in order to obtain the lowest energy structures and to understand the growth behavior. In the next step, these optimized geometries are used to calculate the binding energy and HOMO-LUMO gap (band gap) of the clusters. In all cases ring type structures are found to be most favorable but for n = 3-6, the ring structures are not planar suggesting that the bonding nature in these cluster has some covalent character.

Various scattering cross section such as differential, integrated elastic, momentum transfer, total cross-sections and spin polarization parameters for both the elastic and total scattering of electron and positron from Re atoms in the impact energy range between 2.0 to 500 eV using the relativistic Dirac equations are studied. The target-projectile interaction is included by real and complex-free optical potentials for obtaining the solutions of Dirac equation for scattered electrons and positron. The Dirac-Fock wave functions have been used to represent the $e^{±}$-Re target atoms. Corresponding theoretical results are obtained from a relativistic approach based on solving the Dirac equation using Hartree-Fock and Dirac-Fock wave functions to calculate cross sections at all the energies measured.

We have made a study of the total ionization cross sections of hydrocarbon molecules (allene, propane) due to electron impact for single ionization. Electron impact ionization cross sections (EIICS) have been calculated from threshold ionization energy to high energy (10 MeV). Along with EIICS calculation the values of collisional parameters are also calculated. The theoretical model, developed by Khare, has been modified to calculate the electron impact ionization cross section for molecules and atoms. The predicted EIICS of allene and propane molecules are compared with other theoretical and experimental data. Present model prevail a high degree of goodness of cross sections to the experimental data.  Adequate comparisons of collisional parameter have been made with other available experimental values.

Based on the specific microstructure of HDDR (hydrogenation, disproportionation, desorption, recombination) grains, that the bivariate model concerning the anisotropy constant $K'_1$ and exchange integral $A'_1$ in defect region, which was put forward. Subsequently, the dependence of magnet coercivity on the intergranular phase thickness $d$ and structure defect thickness $r_0$ was studied. The results showed that the coercivity, $H_c,$ increases with increasing $d,$ for the $r_0,$ the anisotropy constant $K_1(0)$ and exchange integral constant $A_1(0)$ at the grain surface taking different values. While $K_1(0)$ and $A_1(0)$ are fixed, $H_c$ enhances with increasing $r_0$ for the same $d.$ On the contrary, for the fixed $r_0$ and $d,$ $H_c$ decreases with increasing $K_1(0)$ or $A_1(0).$ The calculated coercivity is in good agreement with experimental results given by others when $d$ takes 1 nm, $r_0$ is in the rang of 2-5 nm, $A_1(0)$ and $K_1(0)$ change in the range of (0.6-0.7) of $A_1$ and $K_1,$ respectively.

We have investigated the structures and properties of the hydrogen bonded complexes formed between HRnCCH and X (X stand for nitrogen, oxygen, water and ammonia) using MP2 (full) theoretical method at the aug-cc-pVTZ-pp for Rn atom and aug-cc-pVTZ for other atoms. In this study, as for the complexes between HRnCCH and X, three stationary structures are located (one annular and two linear structures) corresponding to the true energy minima on the potential energy surface. In these complexes, the red shift of the H-Rn stretch in the linear structure $C_{XA},$ whereas the blue shift of the H-Rn stretch in the structure linear $C_{XB}$ and the structure circular $C_{XC},$ the biggest red shift is -35.71 $cm^{-1}$ in $C_{NH3A}$ and the biggest blue shift is 76.45 $cm^{-1}$ in $C_{H2OB}.$  In addition, we found a tremendous red shift in $C_{H2OC}$ (-154.7 $cm^{-1}$ in O-H bond) and $C_{NH3A}$ (-96.15 $cm^{-1}$ in C-H bond). The most stable structure is the circular structure between HRnCCH and $H_2O,$ whose interaction energies is -27.4 kJ/mol. The origin of the frequency shift and charge transfer in these complexes has been analyzed by the natural bond orbital analysis and atom in molecule. The natural bond orbital analysis indicates the $C\rightarrow \sigma^*_{H-Rn}$ orbital interaction plays a key role in the stabilization energy. The atom in molecule shows the largest the absolute value of V = 0.0220 a.u and the most negative the value of H = -0.0055 a.u corresponding the most stabilization of the circular structure between HRnCCH and $H_2O.$

We apply BBK, DS3C model and the new modified Sommerfeld parameters of the present DS3C model to calculation of the triple differential cross sections (TDCS) for electron impact ionization of helium in the perpendicular plane symmetric geometry. The results of the present are compared with the measurements and those of other theoretical models. It was found that the present results give a better description for the experimental data and the dynamical screening effects are strong in this geometry. The influence of the Sommerfeld parameters on the triple differential cross sections is also analyzed and discussed in the perpendicular plane geometry.

We investigate the spin current through a molecular quantum dot (MQD) irradiated with a rotating magnetic field and an oscillating magnetic field by nonequilibrium Green's function. The rotating magnetic field rotates with the angular frequency $\omega_r$ around the $z$-axis with the tilt angle $\theta$, and the time-oscillating magnetic field is located in the z-axis with the angular frequency $\omega$. Different behaviors have been shown in the presence of electron-phonon interaction (EPI) which plays a significant role in the transport. The spin current displays asymmetric behavior as the source-drain bias $eV=0,$ novel side peaks or shoulders can be found due to the phonon absorption and emission procedure, and the negative spin current becomes stronger as the parameter $g$ increases. However, the spin currents display the same magnitude and the same oscillation behavior in the region $\mu_0B_1>3\Delta$ regardless of the parameter $g.$

We investigate the plasmon resonance of a touching gold cylinder arrays surrounded with air or dielectric. We show that the plasmon resonance is tunable by modulating the cylinder radius, the cylinder layer and refractive index of the dielectric. It is found resonance peak blue-shifts and splits as the gold cylinder radius reduces, width of the resonance peak gets much smaller as layer increases, and resonant peak red-shifts noticeably as dielectric refractive index increases. Based on electric field distributions at the resonance wavelengths we reveal the mechanism of the transmission enhancement. These phenomena are helpful for the design of potential optics devices.

First-principles investigation on the inelastic electron tunneling spectra of bi-oligophenyleneethynylenes (OPEs)- monothiol molecular junctions is performed. It is demonstrated that the inelastic electron tunneling spectra are very sensitive to the deviation, stagger or separation of the two molecules in the bimolecular junctions. To some extent, the spectra of bimolecular junctions can present similar characteristics as a single OPE-monothiol molecular junction, which reflects the neglectable interaction between two molecules. When the overlap between the two molecules is relatively strong, out of plane vibration modes are active in the spectra and provide more intermolecular tunneling paths for electrons.

The nucleation of graphene on Ni surface, as well as on the step, is studied using a tight binding method of SCC-DFTB. The result demonstrates that the fcc configuration has the lowest total energy and thus is the most stable one compared to the other two structures when benzene ring is absorbed on the Ni(111) surface. The activity of marginal growth graphene's carbon atoms decreases from the boundary to the center, when they are absorbed on the substrate. Graphene layer can grow continuously on step surface formed by intersection of Ni(111) and Ni(1$\bar{1}$1) surface. Meanwhile, a mismatch will occur between the graphene layer and Ni surface and thus leads to flaws when the layer grows larger. Reducing the mismatch between the graphene and the step surface will benefit the growth of graphene of large area and high quality.