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.

Wettability of net C, net W and net Y: a molecular dynamics simulation study

“…It should be noted that this force field gives a value of 128.76° for the contact angle of water on graphene, which is very close to the experimental value. 17 The contact angle trend is net Y > net W > net C, which corresponds to these allotropes' energy trend. The point that justifies the contact angle trend is the carbon substrates' atomic density.…”

“…Such a layered structure has already been seen for drops on graphene and penta-graphene. 17 Although the Leonard-Jones potential predicts only two or three peaks, 14 the reactive potential indicates a greater number of peaks, demonstrating the fact that the water droplet's configuration on the substrate is layered. Although the Leonard-Jones potential produces only two or three peaks, 21 the layer structure has been extracted empirically, 22 both in terms of molecular dynamics simulations 23 and density functional theory.…”

“…The contact diameter for a water drop on graphene is 39.35 Å. 17 Because the contact angle for net C is the smallest, the contact diameter for net C is the largest. The contact angle for net Y is the largest and therefore the contact diameter for net Y is the smallest.…”

“…This force field has already been used to study wettability. 17 A canonical ensemble with 2000 water molecules at a temperature of 300 K is used. Because all three allotropes are stable at 300 K, the simulations are performed at this temperature.…”

Current Understanding of the Wettability of MXenes

“…Molecular dynamics (MD) simulation deals with the N‐body situations by solving Newton's equation of motions for a system containing a group of particles interacting with each other, providing valuable information regarding the properties of materials based on the well‐defined forcefields. [ 36 ] It has already been extensively used to analyze the wetting properties of various 2D materials, including graphene and its derivatives (e.g., graphene oxide [ 37 ] and penta‐graphene [ 38 ] ). Furthermore, MD simulation was proved to be compatible with the MXene‐based systems, where the charge storage mechanism for Ti 3 C 2 T x in acidic electrolyte was elucidated by investigating the interaction between the MXene sheets and the water molecules nearby.…”