Local ice-like structure at the liquid water surface (2202.05883v1)

Abstract: Experiments and computer simulations have established that liquid water's surfaces can deviate in important ways from familiar bulk behavior. Even in the simplest case of an air-water interface, distinctive layering, orientational biases, and hydrogen bond arrangements have been reported, but an overarching picture of their origins and relationships has been incomplete. Here we show that a broad set of such observations can be understood through an analogy with the basal face of crystalline ice. Using simulations, we specifically demonstrate that water and ice surfaces share a set of structural features suggesting the presence of nanometer-scale ice-like domains at the air-water interface. Most prominent is a shared characteristic layering of molecular density and orientation perpendicular to the interface. Similarities in two-point correlations of hydrogen bond network geometry point to shared ice-like intermolecular structure in the parallel direction as well. Our results bolster and significantly extend previous conceptions of ice-like structure at the liquid's boundary, and suggest that the much-discussed quasi-liquid layer on ice evolves subtly above the melting point into a quasi-ice layer at the surface of liquid water.