在石墨夾層間的奈米水：彈性SPC/E模型

Abstract

在本論文中，使用LAMMPS模擬器對在平行石墨板夾層中的彈性水模型做分子動力模擬，並研究在石墨夾層間距從20Å到7Å的系統中，水分子的局部結構以及動力學。 模擬結果顯示，每一種系統的水分子皆會有分層的現象，且隨著石墨夾層間距縮小會使得系統中的水分子更傾向固體結構，不同的石墨夾層間距亦對其氫鍵狀態有所影響。在同一個系統中，每一層的水分子結構也不盡相同，在靠近石墨板的最外層，水分子大致上可分成分子平面垂直或平行石墨板的兩種方向。我們發現各層水分子在平行及垂直於石墨板方向上有不同的運動行為。當石墨夾層間距縮小，各水層的氧原子間的平移速度頻譜會有藍移現象；而水分子內部的運動頻譜在夾板間距7Å的系統中，OH鍵伸縮運動的頻譜會出現兩個峰值。

In this thesis, we performed molecular dynamics (MD) simulations by LAMMPS simulator to study the structural and dynamic properties of flexible water model between parallel graphite plates with separation distances from 20 to 7Å. The simulations indicate that water molecules in each system are stratified, and tend to behave more solid-like as the confinement distance between graphite plates decreases. Different distances between graphite plates have an influence on the hydrogen bond configuration as well. In the same system, water molecular structures belonging to different layers would not be the same. In the layer nearest to the graphite plate, water molecule structures could be roughly classified into two directions according to the molecular plane perpendicular or parallel to the graphite plates. We found that the water molecules in different layers have various dynamical behaviors in the direction parallel or perpendicular to the graphite plates. By decreasing the distance between graphite plates, a blue shift in the intermolecular power spectrum of velocity autocorrelation function of oxygen atoms was observed in all water layers. And the intramolecular spectrum of OH-bond stretching motion split into two peaks with the confinement distance getting reduced to 7Å.