レプリカ交換分子動力学法を用いたナノスリット内の多層氷の結晶構造の探索

抄録

Ices show many crystal structures depending on the external conditions, such as temperature, pressure. It is known that, when water is confined to the environment at the nanoscale, they show peculiar crystal structures not seen in bulk water due to the spatial limitation. In this research, we focus on the system confined to the slit nanopore, which is called quasi-2-dimensional (Q2D) system. Several Q2D ices are reported in the literature, and they are classified by the number of layers, such as monolayer (ML) ices, bilayer (BL) ices, trilayer (TL) ices, and multilayer ices. Until now, many ML ices and BL ices are reported in the literature. However, few TL ices or multilayer ices are reported in spite of their high structural degrees of freedom. Therefore, we performed molecular dynamics (MD) simulation of water in slit nanopore and explored crystal structures of Q2D TL or multilayer ices. In order to explore the crystal structure of ice, we used replica exchange method, which enables us to explore various states of the system efficiently without being trapped in local minimum. Performing replica exchange MD simulations, we found several TL ices and multilayer ices, and revealed their peculiar crystal structures.