报告主题： First-Principles Investigations of Water Adsorption on h-BN Nanomesh Surface and Anomalous Water Diffusion in Salt Solutions (硼氮纳米表面的水吸附和盐溶液里的水扩散——第一原理计算研究)
报 告人：丁云 博士 (瑞士ETH Zurich）
报告时间：2014年11月27日（周四)10:00
报告地点：校本部G309
主办部门：理学院物理系
邀 请人：任伟教授
摘 要：
The boron nitride nanomesh is a corrugated structure with a periodicity of 3.2 nm, which is formed self-assembly by decomposition of borazine on a clean Rh(111) surface at high temperature. By means of density functional theory (DFT) calculations, we are able to reproduce the nanomesh structure. The agreement between simulation and experiment is confirmed by scanning tunneling microscope (STM) images and projected density of states. We study water and nano-ice clusters observed in the nanomesh pore after dosing water to the surface in experiments. The simulation gives insights into the trapping effect of the corrugated structure as well as the properties of the hydrogen bond network. Through the comparison of STM images and by the analysis of the dipole moment distributions, we are able to identify the structures observed in the experiments.
Understanding the effect that ions have on the structural and dynamical properties of water has been a subject of numerous experimental and theoretical studies. Recent nuclear magnetic resonance (NMR) experiments have shown that water self-diffusion (Dw) increases in CsI solution, while decreases in NaCl solution. Due to the fact that classical simulations failed to reproduce this trend, we study 3M CsI, 3M NaCl solutions and pure water using state of the art ab initio MD (AIMD) simulations and we find that AIMD simulations qualitatively reproduce the trends observed in experimental Dw. Our analysis of various dynamical properties show there is a characteristic dynamic heterogeneity in the water ensemble that is present in the AIMD but absent in the empirical simulations.