Water plays a critical role in various aspects of our lives, ranging from basic metabolic activities at micro‐
scopic scales to numerous industrial applications at macroscopic scales. The peculiar thermo‐physical proper‐
ties along with the unusually large dielectric constant of water over macroscopic scales on the one hand and
the emerging intriguing features over microscopic scales on the other are engaging the attention of researchers
across disciplines.
Classical Molecular Dynamics (CMD) simulations have predicted a wealth of structural, dynamical, and di‐
electric features exhibited by water under nanoscale confinement that differs from bulk properties. Confine‐
ment of water over these microscopic scales occurs in nature under biological and geological scenarios. With
the advent of lower dimensional structures such as Graphene, hexagonal Boron Nitride and MXenes having ex‐
otic properties, possibilities for exploring the properties of confined water under these structures has expanded
the scope of research significantly. Some of these observations like formation of square ice like structure under
monolayer confinement and reduction of dielectric constant have been reported in the literature [1, 2]. Such
abnormal behaviour of water not only depends on the geometry of confinement but also on the nature of con‐
fining materials.
Many of these features depend on the details of the interatomic potentials between water molecules and
at the interface between water and the confining ‘wall’. Over the years, a multitude of atomic models for
liquid water have been developed, each catering for a specific requirement. Variations in the parameters of
water‐water interaction potentials have led to differences in computed properties under bulk as well as under
confined conditions [1]. Thus, the choice of potential parameters plays a significant role in establishing the re‐
sults from CMD simulations. Similarly, the dielectric constant has been computed to be around 80 using the
Fluctuation‐Dissipation theorem on data from CMD simulations of bulk water at room temperature. Not sur‐
prisingly, computations on CMD simulations of confined water indicate that the dielectric response of confined
water is anisotropic and inhomogeneous. Some of the studies have reported extremely low dielectric constant
(ϵr≈2) when water is confined within channels of width around a nano meter [2]. While the reason for the re‐
duction in dielectric constant of confined water is still debated [3], CMD simulations under an external electric
field have shown that the reduction in ϵr is not unique to water but a universal property associated with polar
fluids [4].
We plan to perform CMD simulations to study the structural and dynamical properties of water confined
by 2D materials of finite lateral extent and specific hydrophobicity. The dielectric properties of confined water
would be studied using CMD simulations under external field. We wish to explore the spatio‐temporal features
of local electric fields and of polarization fluctuations to understand the anisotropy and inhomogeneity in the
dielectric property of confined water. The influence of the edges of the confining material on the structural,
dynamical, and dielectric properties of water would be investigated.
References
[1] Jeet Majumdar et al. “Dielectric Profile and Electromelting of a Monolayer of Water Confined in Graphene
Slit Pore”. In: J. Phys. Chem. B 125.24 (2021), p. 6670.
[2] Hossein Jalali et al. “Abnormal Dielectric Constant of Nanoconfined Water between Graphene Layers in the
Presence of Salt”. In: J. Phys. Chem. B 125.6 (2021), p. 1604.
[3] Jean‐Francois Olivieri, James T Hynes, and Damien Laage. “Confined Water’s Dielectric Constant Reduction
Is Due to the Surrounding Low Dielectric Media and Not to Interfacial Molecular Ordering”. en. In: J. Phys.
Chem. Lett. (2021), p. 8.
[4] Mohammad H. Motevaselian and Narayana R. Aluru. “Universal Reduction in Dielectric Response of Confined
Fluids”. en. In: ACS Nano 14.10 (2020), p. 12761.