Adyant Agrawal

Water at solid interfaces: Molecular insights into crystal growth and graphene suspensions

Within a nanometre of a solid, water no longer behaves as a bulk fluid. Its structure and
dynamics are modified over several molecular layers. We examine how these interfacial
effects influence two systems: salt crystals growing from supersaturated solution and
graphene nanosheets in shear flow.
Salt crystal growth is a fundamental process in both the environment and engineering
systems, yet the molecular mechanisms controlling crystal growth remain incompletely
understood. Using multi-microsecond molecular dynamics simulations, we grow NaCl, KCl
and Na2SO4 on pre-existing crystal surfaces at controlled supersaturation. Although the
three salts grow at similar rates, their morphologies differ: preferential water adsorption in
NaCl and Na2SO4 produces rough, multilayered crystals [1]
.
At graphene surfaces, water slips rather than sticking. Combining molecular dynamics with
continuum theory, we find that graphene suspensions can have a negative intrinsic
viscosity for aspect ratios above about 5.5. Hydrodynamic slip reduces viscous dissipation
and holds the nanosheets near-aligned with the flow [2]. In both systems, the macroscopic
response depends on interfacial water, which is absent from the classical descriptions of
crystal growth and suspension flow.

[1] A. Agrawal, S. Gravelle, C. Holm, & A. Schlaich, J. Chem. Phys. 163, 24 (2025)
[2] A. Agrawal, C. Kamal, S. Gravelle, and L. Botto, ACS Nano 19, 44 (2025)