Graphene confinement effects on melting/freezing point and structure and dynamics behavior of water

• Graphene effects on the phase transition temperature of water and ice confined between two graphene sheets is investigated.
• The phase transition temperature of the confined ice-water mixture is 29 K less than the non-confined ice-water system.
• Coordination number of water at phase transition temperature in the bulk and confined systems, are 4.9 and 6.2, respectively.
• Maximum accumulation of water molecules is observed in the distance of 2 Å from the graphene sheets.

In this work, the melting/freezing point of confined water between two graphene sheets was calculated from the direct coexistence of the solid-liquid interface. Also, molecular dynamics simulation of confined liquid water-ice between two graphene sheets was applied. The phase transition temperature of the confined ice-water mixture was calculated as 240 K that was 29 K less than the non-confined ice-water system. In order to study the behavior of water molecules at different distances from the graphene sheets, 5 regions were provided using some imaginary planes, located between two graphene sheets. The obtained simulation results showed that water molecules located in the region near each graphene sheet with the thickness of 2 nm had a different behavior from other water molecules located in other regions. The results demonstrated that water molecules in the vicinity of graphene sheets had more mean square displacements than those in the middle regions.

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