Wettability of Penta-Graphene: A Molecular Dynamics Simulation Approach

Abstract

Penta-graphene (PG), an allotrope of carbon, which has recently been discovered, has special properties. Although its electrical and mechanical properties have been well studied, its wettability properties are unknown. In this research, the reactive molecular dynamics has been used to investigate and compare the wettability properties of PG and graphene (G). The simulation results show that PG is a hydrophobic substrate with a contact angle of 134.63°. The reactive force field used in this research produces 128.76° for the water contact angle on G, which is exactly equal to the experimental value. The drops are completely layered on PG and G. However, the separation of the layers on G is better, which is due to the lower translational motion of droplets. In most layers, the average surface density of water molecules on PG is higher than that on G. Also, the droplet diameter on PG is smaller than that on G, which is compatible with the contact angle. Calculation of the order parameter shows that the tetrahedrality of water molecules on PG is greater than that on G. Due to the lower effect of PG on the droplet, the tetrahedral structure of water molecules is preserved. Hydrogen bonding and the number of water molecules at the interface were studied. The results demonstrate that the number of hydrogen bonds of water molecules on G is twice that of PG. The number of water molecules at the water–G interface is more than that at the water–PG interface. Another interesting result is that the displacement of the droplet on PG is 2.8 times that of G. This fact depends on the potential energy surface of the substrate. By scanning the potential energy surface for both substrates, the height of the energy barrier for droplet motion has been estimated, and the results are consistent with the simulation results.