At solid/water interfaces, the polar nature of water and the charge of salt ions generate strong electric fields, inducing significant electronic polarization of the solid surface. We developed polarizable force fields to accurately model these effects at boron nitride–water–ion interfaces, including planar hBN and confined BNNT systems. Using these force fields [Luo et al. (2024)], our MD simulations predicted a water contact angle of 83.1°, closely matching the experimental value of 79.0°. We also found that polarization strongly affects ion adsorption: K⁺ is repelled and I⁻ is attracted to the hBN surface, consistent with ab initio MD results. In contrast, non-polarizable models fail to capture this behavior, significantly overestimating ion adsorption energies by over 12 kcal/mol [Luo et al. (2025)].

Ice crystallization in quiescent water has been extensively studied in the literature.  However, in practical applications, the formation of ice may be associated with a water flow, which generates a shear and may greatly affect the crystallization process.  Little work has been conducted to understand how a shear rate affects ice nucleation rate and growth rate.  

Herein, we investigate homogeneous ice nucleation rate [Luo et al. (2020)] and ice growth rate [Luo et al. (2019)]under shear through MD simulations.  It is found that both nucleation rate and growth rate increase with shear rate, and reach maximum values at intermediate shear rates.  Such behavior is determined by two distinct effects of shear rates.

For ice nucleation:  First, shear increases the free energy barrier, hindering the nucleation of ice.  Second, shear enhances the mobility of water molecules, promoting the formation of ice crystals.  These two effects compete, leading to a maximum nucleation rate at an intermediate shear rate.  For ice growth, the ice growth rate is mainly determined by the dynamics of the hydrogen bond network.  On the one hand, shear can break the hydrogen bond in liquid, which causes the reorganization of water molecules at the liquid-ice interface, leading to the formation of ice.  On the other hand, shear destabilizes the water-ice hydrogen bond, hindering the growth of ice.  At low shear rates, the ice growth rate increases with the shear rate because the former effect is important.  At higher shear rates, the latter effect becomes dominant and the growth rate decreases with the shear rate. 

The results of this work provide useful information about the formation of ice under shear and offer insights into regulating ice crystallization through water flow. 

During the crystallization of seawater, salt ions tend to be expelled by the ice crystals, which is referred to as ion rejection.  The ion rejection has attracted great attention in the past decade due to its important roles in many fields, such as freeze desalination, the movement of ocean circulation, and deep water formation.  However, little work has been conducted to explore the mechanism of ion rejection at the molecular level.

Herein, we conduct MD simulations to investigate the ion rejection upon the freezing of NaCl aqueous solutions [Luo et. al (2021)].  It is found that the hydration energy of Na+ and Cl- with water is stronger than that with ice, which is the fundamental reason for the ion rejection.  However, the free energy minima at the ice-water interface attract ions and may cause ion trapping in the ice.  At high temperatures, the strong thermal fluctuation assists ions to overcome the free energy barrier and diffuse to water phase, and consequence increases the ion rejection.  Furthermore, the rejection rate of Na+ is higher than that of Cl-, which is caused by the relatively large hydration energy difference between Na+-water and Na+-ice interactions. 

In previous works, the calculation of  forces acting on particles suspended in gases is based on the assumption that the interaction between gas molecule and particle is rigid-body collision. For micro-sized particles, this is physically meaningful and the results are consistent with experiments. However, the rigid-body collision assumption becomes questionable as the particle size decreases to nanoscale.  

Therefore, we derived the ananalytical formula for the lift force [Luo et al. (2016a); Luo et al. (2016b); Luo et al. (2018) ] and thermophoretic force [Wang et al. (2017)] on the basis of gas kinetic theory by taking into account gas-particle intermolecular interactions. Our theory includes the previous, rigid-body collision based formula as a special case.