A Theoretical Study of a Single-Walled ZnO Nanotube as a Sensor for H_2 O Molecules

We have studied the property of single-walled ZnO nanotubes with adsorbed water molecules, and theoretically designed a new sensor for detecting water molecules using single-walled ZnO nanotubes using a combination of density functional theory and the non-equilibrium Green's function method. Details of the geometric structures and adsorption energies of the H 2 O molecules on the ZnO nanotube surface have been investigated. Our computational results demonstrate that the formation of hydrogen bonding between the H 2 O molecules and the ZnO nanotube, and adsorption energies of the H 2 O molecules on the ZnO nanotube are larger than the adsorption energies of other gas molecules present in the atmospheric environment. Moreover, the current-voltage curves of the ZnO nanotube with and without H 2 O molecules adsorbed on its surface are calculated, the results of which showed that the H 2 O molecules form stable adsorption configurations that could lead to the decrease in current. These results suggest that the single-walled ZnO nanotubes are able to detect and monitor the presence of H 2 O molecules by applying bias voltages.     

Time-Dependent Local Density Approximation Calculations for Absorption Spectra of Small Carbon Clusters

Absorption spectra for Cn clusters (n = 2-8) are calculated using an adiabatic time-dependent density functional formalism within the local density approximation (TDLDA). We compare the calculated spectra with those computed using a simple local density approximation approach. It is readily observed that the TDLDA spectra display a significant blue shift with respect to the Kohn-Sham eigenvalue spectra. The calculated spectra exhibit a variety of features that can be used for comparison against future experimental investigations. We also obtain a significant threshold absorption, which can distinguish different ground states of the carbon clusters.     

聚合物纳米容器的研究进展

聚合物纳米容器由于具有许多潜在的用途和优势,近年来为许多研究小组关注.本文简要概述了高稳定性聚合物纳米容器的制备技术和智能型聚合物纳米容器的释放途径及机理。     

Au-MgB2-Au纳米结点的负微分电阻效应

运用密度泛函理论结合非平衡格林函数的方法对MgB₂直线原子链与两半无限Au(100)电极构成纳米结点的电子输运特性进行了第一性原理计算．在模拟Au-MgB₂-Au纳米结点的拉伸过程中,计算了结点在不同距离下的结合能与电导．结果发现结点的Au?B键长为1.90 ?,B-Mg键长为2.22 ?时,结合能最大,结构最稳定,此时结点平衡电导为0.51G₀ (G₀=2e²/h)．通过计算投影态密度发现电子通     

Adjustable half-skyrmion chains induced by SU(3) spin-orbit coupling in rotating Bose-Einstein condensates

The ground state properties of the rotating Bose-Einstein condensates (BECs) with SU(3) spin-orbit coupling (SOC) in a two-dimensional harmonic trap are studied. The results show that the ferromagnetic and antiferromagnetic systems present three half-skyrmion chains at an angle of 120° to each other along the coupling directions. With the enhancement of isotropic SU(3) SOC strength, the position of the three chains remains unchanged, in which the number of half-skyrmions increases gradually. With the increase of rotation frequency and atomic density-density interaction, the number of half-skyrmions on the three chains and in the regions between two chains increases gradually. The relationships of the total number of half-skyrmions on the three chains with the increase of SU(3) SOC strength, rotation frequency and atomic density-density interaction are also given. In addition, changing the anisotropic SU(3) SOC strength can regulate the number and morphology of the half-skyrmion chains.     

First—Principle Calculations for Scanning—Tunelling—Microscopic Images of a Monolayer Graphite Surface

We have applied first-principle total-energy electronic structure calculations in the local density approximation to calculate the scanning tunnelling microscopy images of a monolayer graphite surface near the Fermi level.The results obtained agree well with the observation.which has not been interpreted before.     

重水分子伸缩振动谱的非线性量子理论计算

用非线性量子理论中的离散自陷方程对蒸汽态和液态重水分子在高激发态下的伸缩振动能谱进行了计算。从中发现重水分子的振动能谱分布具有许多有趣的特点。计算所得到的结果对研究重水在高压状态下的特性具有重要的应用价值。     

高压下金属铌熔化曲线的分子动力学模拟

铌作为一种高熔点的金属,广泛应用于制作合金材料. 铌的高温高压熔化曲线对于铌基合金的实际应用具有重要影响,但目前还未被成功研究. 本文中,我们采用铌目前已有的嵌入原子相互作用势函数（EAM）,通过经典的分子动力学方法,模拟了铌的熔化曲线. 两相法和改进Z方法的熔化曲线几乎完全一致,与Z方法的结果稍有差异. 我们也比较了尺寸效应对铌熔化曲线的影响. 我们认为,铌的现有的势函数描述其高压特性时不再适合,后续需要构建精确的温度和压强依赖的相互作用势函数来研究铌的高压特性.     

Structural and Thermodynamic Properties of Gallium Arsenide with Hexagonal Wurtzite Structure from First-Principles Analysis

A first-principles plane wave method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation （GGA） is performed to calculate the lattice parameters, the bulk modulus Bo and its pressure derivative B~o of the hexagonal wurtzite GaAs （w-GaAs） by the Cambridge serial total energy package （CASTEP）. Our calculations show that the most stable structure of the w-GaAs corresponds to the axial ratio c/α = 1.651 and the internal parameter u = 0.374, consistent with other theoretical results. Also, the thermodynamic properties of the w-GaAs are investigated from the quasi-harmonic Debye model. The dependences of the normalized lattice parameters α/α0, c/c0, the axial ratio c/α, the normalized volume V/V0, the heat capacity Cv and the thermal expansion α on pressure P and temperature T are also obtained successfully.     

Elastic Properties of Rutile TiO2 at High Temperature

Dependence of elastic properties on temperature for rutile TiO2 is investigated by the Cambridge Serial Total Energy Package （CASTEP） program in the frame of density function theory （DFT） and the quasi-harmonic Debye model The six independent elastlc constants of rutile TiO2 at high temperature are theoretically obtained for the first time. It is found that with increasing temperature, the elastic constants will decrease monotonically. Moreover, we successfully obtain the polycrystalline moduli BH and GH, as well as the Debye temperature ⊙D.