The Frantz–Nodvik model was extended to propagate pulse through a double-pass laser amplifier and to study beam-interaction effects on the output-energy fluence and gain factor according to the distance between two beams. We also obtained the necessary approximation equations for the saturation state and small input pulse. The results show that minimum output energy and gain occur when two beams completely coincide. The comparison between numerical, analytical, and empirical results demonstrates a good correspondence.

The scattering problem of three particles interacting via Coulomb potentials is studied using generalized parabolic coordinates. The scattering solutions are obtained by solving a driven equation. The ‘perturbation’ operator appearing in the driven term is the non-orthogonal part of the kinetic energy operator. The approximated solution appearing in the driven term is the product of two two-body Coulomb wave functions. As a test for our proposal, a simple two-dimensional model problem has been solved numerically by using so called parabolic quasi-Sturmian basis representation. Convergence of the solution has been obtained as the basis set is enlarged.

The structural, elastic, and electronic properties of zirconium nitride (ZrN) and hafnium nitride (HfN) are investigated by first principles calculation with density functional theory. The obtained cubic NaCl structure is energetically the most stable structure at ambient pressure. A pressure induced structural phase transition from B1 to B2 phase is predicted. The estimated superconducting transition temperature $(T_c)$ of ZrN and HfN are 9.17 K and 8.66 K respectively. As pressure increases, the superconducting transition temperature also increases.

The structural stability of nickel oxide (NiO)$_n$ $(n=1$~$7)$ nanoclusters were studied using Gaussian 03W program package with B3LYP/6-31G level basis set. It is observed that the ring structure is more stable in most cases compared to other structures( Linear and 3D). For $n > 6$ the 3D structure is no longer stable. From the optimization results of (NiO)$_n$ clusters it is found that when the atoms in the cluster increases it leads to the increase in the stability. The dipole moment of each cluster is also studied which shows that the dipole moment depends upon the arrangement of atoms in the cluster. The HOMO LUMO gap, ionization potential, electron affinity and binding energies of Nickel Oxide clusters have been calculated and reported.

At ab initio level, time-dependent hybrid density functional theory and response theory have been applied to study the solvent effect on the geometrical and elctronic structure as well as one- and two-photon absorption (TPA) properties of 2,2':6',2"-terpyridine-based chromophore L. It is found that solvatochromic shift of charge-transfer (CT) appears nonmonotonic behavior with regard to the polarity of solvent. Besides, the one-photon absorption (OPA) strengths are enlarged slightly and are more dependent on the optical dielectric constant. The TPA cross sections are enhanced when considering solvent effect compared to that in gas phase and the TPA cross sections show an increasing trend with the increase of solvent polarity. All the theoretical results are in reasonable agreement with experimental data.

Initial configuration plays an important role in molecular dynamics (MD) simulation. Based on ab initio MD simulation used widely, we here first introduce a global search method for the ground state structure of clusters. We think that during a simulation, each type of atoms in cluster should be in equivalent sites when we choose the initial configuration. Thus, our proposal is an improvement in eliminating the ``unequal" in traditional annealing technology, and the results should be more convinced. Moreover, our method can make us obtain all possible structures of clusters, and also get some new structures, which are left out by previous studies. As an illustrative application, we here examine the $S_6$ cluster and found many structures (e.g. $D_{3d},$ $C_{2v},$ $D_{3h},$ $C_s$ and $C_1$). The geometrical parameters and vibrational frequencies are in agreement with experimental values.

Based on the Gupta-type semi-empirical inter-atomic many-body potential, the melting behaviors of the $Al_{196}$ cluster are systematically studied by using the molecular dynamics method combined with the annealing and quenching techniques. Our simulation results show that from different initial structures one can observe quite different melting behaviors. From a relatively low-energy stable geometry, two peaks occur clearly in the heat capacity curve; But only one peak dominates the heat capacity curve if starting from the ground-state or its closer low energy structures. Reasons of the different melting properties of the Al196 cluster are explored by analyzing the energy distributions of the simulated quenching structures of $Al_{196}$ at different temperatures.

The structural, stability and elastic property of single-walled ZnS nanotubes (SW-ZnS NTs) with armchair and zigzag forms were investigated using first-principles approaches. We have investigated a size dependence of stability and elastic modulus in SW-ZnS NTs. It is found that both the stability and the Young’s modulus are decrease dramatically with increasing diameter and proportional to the Zn-S bond length.