第一性原理研究氧在Ni(111)表面上的吸附能及功函数

采用基于密度泛函理论（DFT）广义梯度近似（GGA）下的第一性原理方法系统地研究了不同覆盖度下O在Ni（111）表面的吸附特性.计算结果表明,O在Ni（111）表面的稳定吸附位为三重面心立方（fcc）洞位,吸附能随着覆盖度的增加而减小,O诱导Ni（111）表面功函数的变化量与覆盖度成近线性关系,并随着覆盖度的增加而增大.同时,通过对电子密度和分波态密度的分析发现：O在Ni（111）表面的吸附使得Ni表面电子向O原子转移,形成表面偶极矩,导致功函数增加;表面Ni原子的3d轨道和O的2p轨道通过耦合、杂化作用形成成键态和反键态,而反键态几乎不被占据,因而O—Ni键相互作用比较强,吸附能较大. 关键词： 表面吸附 密度泛函理论 吸附能 功函数     

本征磁性拓扑绝缘体MnBi2Te4电子结构的压力应变调控

由于MnBi2Te4电子结构具有对晶格常数的改变相当敏感的特性,本文采用基于密度泛函理论的第一性原理方法对MnBi2Te4反铁磁块体的电子结构施加等体积应变调控.研究发现体系能带结构在材料等体积拉伸和压缩作用下变化灵敏,体系出现绝缘体-金属相变.特别地,当施加特定应变后导带和价带在Γ处出现交叉,体系呈零带隙状态.在此应变下仍可观察到能带反转的现象,具有非平庸的能带拓扑性质.根据不同应变下的电荷密度图,发现等体积应变会影响体系七倍层层间距,其中等体积压缩和拉伸应变可分别增大和减小Te原子层间距,表明等体积压缩有利于降低反铁磁层间耦合.通过等体积压力应变调控,掌握了MnBi2Te4的电子结构的变化规律,这对本征磁性拓扑绝缘体MnBi2Te4的物性研究和实验制备具有重要的指导意义.     

Effect of oxygen vacancy defect on the magnetic properties of Co-doped ZnO

The influence of oxygen vacancy on the magnetism of Co-doped ZnO has been investigated by the first-principles calculations.It is suggested that oxygen vacancy and its location play crucial roles on the magnetic properties of Co-doped ZnO.The exchange coupling mechanism should account for the magnetism in Co-doped ZnO with oxygen vacancy and the oxygen vacancy is likely to be close to the Co atom.The oxygen vacancy (doping electrons) might be available for carrier mediation but is localized with a certain length and can strengthen the ferromagnetic exchange interaction between Co atoms.     

Magnetic and Ferroelectric Properties of BiCrOa from First-Principles Calculations

The electro,tic, magnetic, and ferroelectric properties of BiCrO3 in C2/c and R3c structure are investigated by first principles calculations. It is found that the easy magnetization axis in C2/c structure is along the b axis, the magnetic order in R3c structure is G-type antiferromagnetic and the easy magnetization axis is along the rhombohedral [111] direction. Berry phase theory predicts that the R3c structure of BiCrOa has a large spontaneous polarization of 73.9 μC/cm2 along the rhombohedral [111] direction.     

在Flash MX中使用ActionScript语言画圆

不少中学物理老师，在使用Flash MX制作圆周运动、带电粒子在磁场中的运动等与圆有关的课件时，无法使用ActionScript语言(以下简称AS)画真正的圆．经过总结，笔者发现他们采用的方法实质都是一样的，就是使用AS中的“MovieClip．cureTO”命令来实现，区别只是在使用时采用了不同的分段方法，以至于无法画出真正的圆．     

从空气劈尖到牛顿环演变过程的课件制作

利用FlashMX设计制作了一个从空气劈尖过渡到牛顿环的演变过程课件，直观地展示了劈尖干涉和牛顿环同属于等厚干涉这一物理实质，从而进一步加深学生对等厚干涉的理解．     

利用数码相机进行白光光谱的拍摄

本文介绍了一种利用数码相机拍摄白光光谱的方法．详细介绍了拍摄过程中器材准备、拍摄过程及照片编辑等步骤．     

Design and optimization of carbon nanotube/polymer actuator by using finite element analysis

In recent years,actuators based on carbon nanotube(CNT) or graphene demonstrate great potential applications in the fields of artificial muscles,smart switches,robotics,and so on.The electrothermal and photothermal bending actuators based on CNT/graphene and polymer composites show large bending actuations,which are superior to traditional thermaldriven actuators.However,the influence of material parameters(thickness,temperature change,etc.) on the actuation performance needs to be further studied,because it is a critical point to the design and fabrication of high-performance actuators.In this work,finite element analysis(EEA) is employed to simulate the actuation performance of CNT/polymer actuator,which has a bilayer structure.The main focus of this work is to design and to optimize material parameters by using computational method.FEA simulation results show that each layer thickness of actuator has an important influence on the actuation deformation.A maximum curvature of 2.7 cm~(-1) is obtained by simulation,which is much larger than most of the actuator curvature reported in previous experiments.What is more,larger temperature change and larger difference of coefficient of thermal expansion(CTE) between two layers will result in larger bending actuation.This study is expected to provide valuable theoretical reference for the design and realization of CNT-based thermal actuator with ultra-large actuation performance.