Wavefunction correction scheme, which was developed as a variance reduction tool for the pure and fixed-node diffusion Monte Carlo (DMC) computations by Anderson and Freihaut, is applied to the DMC computations of fermions without using the fixed-node constraint. This technique is found to be suitable for the non fixed-node calculations because of the significant decreases observed in the computation efforts in the benchmark computations for calculating results with certain statistical error values.

The structures and elastic constants of face-centered-cubic (fcc) structured nickel at high temperature have been calculated for the first time using molecular dynamics (MD) with the direct method and the quantum Sutton-Chen (Q-SC) potential. The obtained thermoelastic constants are in excellent agreement with the experiment data. Calculated results for the radial distribution function show that the short-range atomic order of low-$T$ is similar to the high-$T$ solid with the applied temperatures. The thermoelastic constants, the bulk and shear modulus as a function of the applied temperature are presented. An analysis for the calculated parameters has been made to reveal mechanical stability of nickel up to 1300 K.

General formalism of special form of Hylleraas correlated wave functions (SFHCWF) is demonstrated in this paper. The adequacy of the SFHCWF in the description as well as of the singlet than of the triplet excited states of two electron systems is also presented in this work. Application of SFHCWF to the calculations of doubly excited nlnl' states (n=2-4) in the helium-like ions is done, using the screening constant by unit nuclear charge method in the framework of a variational procedure. Comparison with various available theoretical and experimental literature values indicates a good agreement.

In light of the semiclassical (Thomas-Fermi) approximation method, the thermodynamic properties of the charged fermion system in homogeneous weak electric field are studied. After deriving the relationship of chemical potential and heat capacity of charged fermion system changed with the external electric field, then the analytic formula of the chemical potential and heat capacity of charged fermion system in the high and low temperature approximation condition is desired. Moreover, the influence of the homogeneous weak electric field on the chemical potential and heat capacity are analyzed.

The structure of a schiff base containing phenylalanine derived from curcumin has been studied by computational simulations using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-311$G^{**}$ level. According to the theoretical calculations of three tautomers, enolic tautomer (A), eneamine tautomer (B) and ketonic tautomer (C), of the schiff base molecular, the geometry, relative stability, charge density population and UV-Vis characteristics of every tautomer are investigated. The calculation results demonstrate that the eneamine tautomer (B) is the most stable one and the stability of tautomers decreases in the sequence: B>A>C. The $\lambda_{max}$ of each tautomer mainly originates from the $\pi$-$\pi$* electronic transition, involving the intramolecular charge transfer. The intramolecular proton transfer caused by electron transitions can result in the interconversion of A and B with a low energy barrier. Water can make the UV-Vis spectra of A and B exhibit remarkable red shift, increasing oscillator strength and absorption intensity. On the contrary, water can make C demonstrate a spectrum without shift, decreasing oscillator strength and absorption intensity.

We present theoretical diamagnetic spectra of Barium using R-matrix method combined with quantum defect theory. The nonhydrogenic character of the spectra is analyzed for Ba. Comparisons are made with similar calculations for hydrogen and with data of  experiments in the l-mixing region and n-mixing region. The result shows that the theoretical results are in good agreement with the experimental ones.

Using the scattering matrix method, we investigate the acoustic phonon transmission and thermal conductance in a quantum waveguide with three stubs at low temperature. It is found that transmission coefficient shows periodic feature and the number of cutoff frequency bands increases with increasing of height h; and the thermal conductance exhibits oscillatory decaying behavior with increasing of the widths between any two stubs; In addition, thermal conductance is sensitive to the width and height of stubs; The results show that changing the geometric parameters of the stubs could provide an efficient way to control the thermal conductance of the proposed micro-structures artificially.

On the condition of electron and LO-phonons strong-coupled, the ground-state energy of polaron has been obtained by using linear combination operator and unitary transformation methods in an asymmetric quantum dot. Quantum transition which causes the changes of the polaron lifetime is occurred in the quantum system due to the electron-phonon interaction and the influence of external temperature effect which is the polaron leap from the ground-state to the first-excited state absorbing a LO-phonon. Numerical calculation is performed and the results show that the ground-state lifetime of polaron increases with increasing the ground-state energy and decreases with increasing the coupling-strength. The ground-state lifetime is extended with the shortening of the temperature. It is also observed that the ground-state lifetime is a decreasing function of the transverse and longitudinal confinement lengths of the quantum dot.

We propose two schemes to realize remote state preparation (RSP). The first scheme is designed to prepare an arbitrary single-particle state in a four-level system with the aid of one bipartite maximally entangled channel, which is then generalized to the second scheme, i.e., RSP for a two-particle state in a four-level system. During the two preparations, one single-particle projective measurement and one two-particle projective measurement are performed respectively. Our results show that the preparation for single-particle or two-particle states can be remotely realized with at least 25% successful probability and unit fidelity. Furthermore, with respect to two special ensembles of the prepared states, i.e., real and equatorial-like, the successful probability can be pushed up to 100%. Hence our probabilistic schemes become deterministic ones.