水分子链受限于单壁碳纳米管结构的密度泛函理论研究

Study on the structure of water chain encapsulated in carbon nanotube by density functional theory

本文采用第一性原理的密度泛函理论,主要以(6,6)Armchair型,(11,0)Zigzag型单壁碳纳米管为研究对象,研究了水分子链在碳纳米管内部吸附的稳定结构,以及结合能随其结构的变化.结果表明:当水分子链受限于碳纳米管内部时,引起碳纳米管直径收缩,这主要是由于水分子链与碳纳米管之间的氢键作用以及范德华弱相互作用所引起的.随着碳纳米管半径的增加,两种单体之间的结合能逐渐减小,但当碳纳米管半径增加至6.78A时,其结合能又有所增加,这是由于在优化过程中,水分子链单体之间的氢键作用大于水分子链与碳纳米管之间的氢键结合能以及范德华力,导致水分子链变化为"book-like"结构.

The structure of water molecules encapsulated in single-walled carbon nanotubes （SWCNTs） was studied using a self-consistent charge density functional tight binding method with dispersion correction. The most interesting and important feature observed is the diameter shrinkage of SWCNTs when water chains are confined inside them. The diameter shrinking of SWCNTs may be due to the van der Waals and H-π interaction between water chains and SWCNTs. The binding energy decreases with the increase of the nanotube radius. But when the radius is increased to 6. 78 ？,the binding energy is a little increased,and the water chain has changed as a ＂book-like＂structure,which suggests that the weak hydrogen bonding in the isolated water chains is larger than the interaction between water chains and the SWCNTs.