网页版快捷绘图程序辅助“二极管伏安特性研究”实验教学

二极管伏安特性研究实验是大学物理实验中的重要基础实验之一。测绘二极管的伏安特性曲线一般采用伏安法进行测量。在实验过程中，学生需要测量二极管两端的电压和流经二极管的电流，并用此来绘制二极管的伏安特性曲线。学生在实验过程中如果能够快捷绘图，以此来及时自检并发现测量数据的问题，对于提高“二极管伏安特性研究”实验的教学效率至关重要。我们采用JavaScript语言编写了快捷绘图程序，为学生提供了快捷网页绘图终端。学生在测量完数据后，通过手机浏览器进入绘图终端，输入测量数据，即可绘制电压和电流的关系曲线(U-I曲线)。“二极管伏安特性研究”实验教学过程中快捷网页绘图终端的引入，可以显著提高学生的学习效率和教师的授课效率。     

First-principles study of helium clustering at initial stage in ThO_2

The clustering behavior of helium atoms in thorium dioxide has been investigated by first-principles calculations. The results show that He atoms tend to form a cluster around an octahedral interstitial site(OIS). As the concentration of He atoms in ThO_2 increases, the strain induced by the He atoms increases and the octahedral interstitial site is not large enough to accommodate a large cluster, such as a He hexamer. We considered three different Schottky defect(SD) configurations(SD_1, SD_2, and SD_3). When He atoms are located in the SD sites, the strain induced by the He atoms is released and the incorporation and binding energies decrease. The He trimer is the most stable cluster in SD_1. Large He clusters, such as a He hexamer, are also stable in the SDs.     

Edge effects on the characteristics of uranium diffusion on graphene and graphene nanoribbons

The first principles density-functional theoretical calculations of U adatom adsorption and diffusion on a planar graphene and quasi-one-dimensional graphene nanoribbons(GNRs) are performed. An energetic preference is found for U adatom diffusing to the hollow sites of both graphene and GNRs surface. A number of U distinctive diffusion paths either perpendicular or parallel to the ribbon growth direction are examined. The edge effects are evidenced by the calculated energy barriers of U adatom diffusion on armchair and zigzag nanoribbons surfaces. The calculation results indicate that the diffusion of U adatom from the inner site toward the edge site is a feasible process, particularly in zigzagGNR. It is viable to control the initial morphology of nuclear carbon material to retard the diffusion and concentration of nuclides.     

A First-Principles Study on the Vibrational and Electronic Properties of Zr-C MXenes

Within the framework of density functional theory calculations,the structural,vibrational,and electronic properties of Zr_(n )C_(n-1)(n=2,3,and 4)and their functionalized MXenes have been investigated.We find that the most stable configurations for Zr-C MXene are the ones that the terminal groups F,O,and OH locate on the common hollow site of the superficial Zr layer and its adjacent C layer.F and OH-terminated Zr_3C_(2 )and Zr_4C_(3 )have small imaginary acoustic phonon branches aroundΓpoint while the others have no negative phonon modes.The pristine MXenes(Zr_2C,Zr_3C_(2 )and Zr_4C_3)are all metallic with large DOS contributed by the Zr atom at the Fermi energy.When functionalized by F,O and OH,new hybridization states appear and the DOS at the Fermi level are reduced.Moreover,we find that their metallic characteristic increases with an increase in n.For(Zr_(n )C_(n-1))O_2,Zr_2CO_(2 )is a semiconductor,Zr_3C_2O_(2 )is a semimetal,and Zr_4C_3O_(2 )becomes a metal.