Edge-Driven Phase Transitions in 2D Ice

TL;DR

This study investigates how electric fields from polar materials influence the phase transitions of 2D water confined between nanoribbons, revealing pathways to control water's crystalline states and flow at the nanoscale.

Contribution

It demonstrates the role of nanoribbon edges, polarity, and interlayer distance in determining 2D water phases using density functional theory and molecular dynamics simulations.

Findings

Crystalline phases depend on nanoribbon edges and polarity.

Phase diagrams show liquid-solid and different crystalline order transitions.

Crystalline order persists under external pressure during water flow.

Abstract

2D water, confined by atomically flat layered materials, may transit into various crystalline phases even at room temperature. However, to gain full control over the crystalline state, we should not only confine water in the out of plane direction but also restrict its in plane motion, forming 2D water clusters or ribbons. One way to do this is by using an electric field, in particular the intrinsic electric field of an adjacent polar material. We have found that the crystalline phases of 2D water clusters placed between two hexagonal boron nitride hBN nanoribbons are crucially determined by the nanoribbons edges, the resulting polarity of the nanoribbons, and their interlayer distance. We make use of density functional theory with further assistance of molecular dynamics simulations to establish the comprehensive phase diagrams demonstrating transitions between liquid and solid phases and between the states of different crystalline orders. We also show that the crystalline orders are maintained when water flows between hBN channels under external pressure. Our results open a promising pathway towards the control of water structure and its flow by the use of the microscopic electric field of polar materials.