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.

The experimental synthesis of biphenylene, a two-dimensional carbon allotrope, theoretically predicted in 1997, took place in 2021.

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The effect of the triple-phase contact line (TPCL) on the wetting phenomenon has been extensively discussed during the past decade. Numerous attempts have also been made to quantify its characteristics based on thermodynamic or mechanical definitions. In this research, molecular dynamics simulation was used to define the term “vicinity of the TPCL” and its effect on the hydrophilic and hydrophobic behaviors of a water nanodroplet. A nanodroplet was placed on a substrate that was modified in a stepwise manner by growing a patch of heterogeneity from either the center of the substrate or from the sides. The relative direction of motion of the TPCL and the patch determined the pathway that the nanodroplet chooses in order to change its wetting regime from hydrophilic to hydrophobic and vice versa. A gradual change occurs when the TPCL and the heterogeneity move in the same direction, and an abrupt change takes place otherwise. In addition to the insights into the wetting phenomenon, the width of the TPCL is also discussed. The obtained data suggest that the effective width of the TPCL, δ, is different inside the perimeter of the nanodroplet from outside of it. Moreover, the value of δ for the abrupt pathway is twice as large as the gradual one. In conclusion, the width, or vicinity, of the TPCL depends on the type of the pathway and the configuration of the substrate-patch system and cannot be treated similarly in both cases.

The mechanical strength of a polycrystalline material can be drastically weakened by a phenomenon known as grain boundary (GB) premelting that takes place, owing to the so-called disjoining potential, when the dry GB free energy $$\sigma _{gb}$$ σ gb exceeds twice the free energy of the solid–liquid interface $$\sigma _{sl}$$ σ sl . While previous studies of GB premelting are all limited to equilibrium conditions, we use a multi-phase field model to analyze premelting dynamics by simulating the steady-state growth of a liquid layer along a dry GB in an insulated channel and the evolution of a pre-melted polycrystalline microstructure. In both cases, our results reveal the crucial influence of the disjoining potential. A dry GB transforms into a pre-melted state for a grain-size-dependent temperature interval around $$T_m$$ T m , such that a critical overheating of the dry GBs over $$T_m$$ T m should be exceeded for the classical melting process to take place, the liquid layer to achieve a macroscopic width, and the disjoining potential to vanish. Our simulations suggest a steady-state velocity for this transformation proportional to $$\sigma _{gb} -2 \sigma _{sl}$$ σ gb - 2 σ sl . Concerning the poly-crystalline evolution, we find unusual grain morphologies and dynamics, deriving from the existence of a pre-melted polycrystalline equilibrium that we evidence. We are then able to identify the regime in which, due to the separation of the involved length scales, the dynamics corresponds to the same curvature-driven dynamics as for dry GBs, but with enhanced mobility.