Ab initio H2O in realistic hydrophilic confinement

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Nanoscience

Background:

• Understanding liquid behavior in nanoscale confinement is crucial for various applications.
• Amorphous silica offers a versatile matrix for creating controlled nanoporous structures.
• Simulating water confined within realistic nanopores presents significant computational challenges.

Purpose of the Study:

• To develop a protocol for the ab initio construction of a realistic cylindrical pore in amorphous silica.
• To characterize the structure and dynamics of liquid water confined within this nanoscale pore.
• To investigate the effects of geometric nanoscale confinement on water's density, structure, hydrogen bonding, and diffusion.

Main Methods:

• Ab initio construction of a cylindrical pore model in amorphous silica.
• Molecular dynamics simulations of liquid water at varying densities within the pore.
• Analysis of water density profiles, radial distribution functions, and hydrogen bond networks.
• Characterization of diffusion coefficients and structural changes near the pore wall.

Main Results:

• The pore induced long-range oscillations in the water density profile, deviating significantly from bulk water.
• Water's tetrahedral structure was altered up to the second solvation shell of the pore wall.
• Confinement weakened and distorted hydrogen bonding at the pore walls.
• Diffusion of water molecules within the pore was significantly slowed down.

Conclusions:

• The study successfully established a realistic nanoscale silica pore model for simulating confined liquids.
• Nanoscale confinement in silica pores profoundly impacts water's structural organization and dynamics.
• These findings provide insights into liquid behavior at the nanoscale, relevant for materials science and chemical engineering.