▎ 摘　　要

As the two-dimensional square ice in graphene nanocapillaries 10 was observed by transmission electron microscopy (TEM), a variety of theoretical methods have been applied to explore this phenomenon. However, a satisfactory model has not yet been described. Here, we investigate the structural properties and phase behavior of the confined water in graphene nanocapillaries by using the ABEEM sigma pi polarizable force field (PFF) with the ABEEM-7P water model and ABEEM sigma pi graphene model. The ordered AB-stacked bilayer and ABA-stacked trilayer square ice samples are acquired in 8.0 and 10.2 angstrom graphene nanocapillaries, respectively, at 298 K at a constant volume. Furthermore, the bilayer and trilayer ices demonstrate rhombus-square-triangular ice as the graphene nanocapillary changes from 7.8 to 8.6 and 10.0 to 11.0 angstrom, respectively. The results yielded by using a fixed charge force field with the SPC/E water model are different from those obtained by ABEEM sigma pi PFF. By changing the constant pressure from 0.5 to 1.5 GPa, the monolayer (bilayer) triangular ice is transformed to bilayer (trilayer) square ice in a 6.5 (9.0) angstrom graphene nanocapillary system. Additionally, the van der Waals interactions, density of the confined water, confinement width, polarization effects, and pressure all play decisive roles in the distribution of the confined water. Our study provides some clues for clarifying the experimental consequences of TEM.