Stability and relaxation in nanostructures: Recent examples with carbon, silicon, and boron
报告人:
Boris I. Yakobson 教授
Departments of Mechanical Engineering and Materials Science, Department of Chemistry, Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX, USA
报告时间:
2007-06-21 15:00
报告地点:
清华—富士康纳米科技研究中心四楼报告厅
主办单位:
清华—富士康纳米科技研究中心
简介:
Yakobson教授将会介绍Rice大学，他的研究小组，他的研究工作等，并希望从清华招收2-3名优秀同学到他的研究组作博士生或博士后。有意向的同学请在演讲结束后同Yakobson教授面谈。下面是演讲的摘要： Science and engineering of nanoscale structures blend the notions and intuition of mechanical engineering with the fundamentally different aspects of solid state physics and quantum chemistry [1]. Through our studies of nano-tubes and wires, we have encountered the situations when such interpenetration can be very useful, but can also be misleading. I will discuss the stability and structure of nearly 1-dimensional wires of silicon and metals, to contrast their makeup to the “no-surface” structure of the carbon nanotubes. The atomistic relaxation paths in the nanotubes are sensitive to the temporal and thermal conditions: the single bond rotations or the brittle unzipping through a series of lattice-trapped states. Combination of quantum-chemistry computations with the probabilistic approach of transition state theory allows one to compare the different channels of relaxation and to determine the strength as a function of time, symmetry, and temperature [2]. Predictions and recent discoveries of superplasticity and coalescence/welding will also be considered in atomistic detail, with particular emphasis of self-repair mechanism, permitting the nanotubes to retain perfection even at harsh conditions [3]. Finally, I will present a structure which emerged as a spin-off of our quest for energy-storage nanocages?the boron backyball B80 [4], whose stability stands out among all other boron clusters, while it also bears striking resemblance to the Fuller’s domes. Either this prediction can ever lead to a branch of boron-fullerene materials is yet to be explored by colleagues-experimentalists. [1] B. Yakobson and R. Smalley, American Scientist 85, 324-337, (1997). [2] T. Dumitrica et al. Proc. Natl. Acad. Sci. 103, 6105-6109 (2006). [3] F. Ding et al. Nano Lett. 7, 681 (2007); F. Ding et al. Phys. Rev. Lett. 98, 075503 (2007). [4] N. Gonzalez et al. Phys. Rev. Lett. 98, 166804 (2007); Nature 447, 4 (2007).
