Effects of Surface Dipole Lengths on Evaporation of Tiny Water Aggregation  

作　　者：王棽 涂育松 万荣正 方海平 

机构地区：[1]Shanghai Institute of Applied Physics,Chinese Academy of Sciences [2]Graduate School of the Chinese Academy of Science [3]Institute of Systems Biology,Shanghai University

出　　处：《Communications in Theoretical Physics》2013年第5期623-628,共6页理论物理通讯（英文版）

基　　金：Supported by National Natural Science Foundation of China under Grant Nos.11175230 and 11105088;National Program on Key Basic Research Project under Grant No.2012CB932400;Shanghai Supercomputer Center of China and Shanghai University Supercomputer (ZQ3000&4000)

摘　　要：Using molecular dynamics simulation, we compared evaporation behavior of a tiny amount of water molecules adsorbed on solid surfaces with different dipole lengths, including surface dipole lengths of 1 fold, 2 folds, 4 folds, 6 folds and 8 folds of 0.14 nm and different charges from 0.1e to 0.9e. Surfaces with short dipole lengths (1-fold system) can always maintain hydrophobic character and the evaporation speeds are not influenced, whether the surface charges are enhanced or weakened; but when surface dipole lengths get to 8 folds, surfaces become more hydrophilic as the surface charge increases, and the evaporation speeds increase gradually and monotonically. By tuning dipole lengths from 1-fold to 8-fold systems, we confirmed non-monotonic variation of the evaporation flux (first increases, then decreases) in 4 fold system with charges (0.1e-0.7e), reported in our previous paper [S. Wang, et al., J. Phys. Chem. B 116 (2012) 13863], and also show the process from the enhancement of this unexpected non-monotonic variation to its vanishment with surface dipole lengths increasing. Herein, we demonstrated two key factors to influence the evaporation flux of a tiny amount of water molecules adsorbed on solid surfaces: the exposed surficial area of water aggregation from where the water molecules can evaporate directly and the attraction potential from the substrate hindering the evaporation. In addition, more interestingly, we showed extra steric effect of surface dipoles on further increase of evaporation flux for 2-folds, 4-folds, 6-folds and 8-folds systems with charges around larger than 0.7e. (The steric effect is first reported by parts of our authors [C. Wang, et al., Sci. Rep. 2 (2012) 358]). This study presents a complete physical picture of the influence of surface dipole lengths on the evaporation behavior of the adsorbed tiny amount of water.

关 键 词：EVAPORATION surficial water WETTABILITY dipole length molecular dynamics 

分 类 号：O561[理学—原子与分子物理]