Model channel ion currents in NaCl-extended simple point charge water solution with applied-field molecular dynamics

Area of Science:

• Computational chemistry
• Physical chemistry
• Materials science

Background:

• Understanding ion transport through nanoporous materials is crucial for applications like desalination and energy storage.
• Atomistic simulations provide detailed insights into the complex mechanisms governing ion flow across membranes.

Purpose of the Study:

• To investigate the current-voltage characteristics of ion flow through a model atomistic channel.
• To determine the influence of ion concentration and applied electric field on channel conductance.

Main Methods:

• Simulated ion current through a rigid, atomistic channel with polar walls using explicit ions and polarizable water models.
• Employed periodic boundary conditions and constant applied electric fields.
• Analyzed 100 ns trajectories under varied concentration and voltage conditions.

Main Results:

• The electric field predominantly drops across the membrane channel, consistent with capacitive models.
• The channel is typically occupied by a single ion, limiting capacity.
• Observed concentration-dependent current-voltage relationships, exhibiting superlinear behavior at high concentrations.

Conclusions:

• Ion transport in such channels is highly sensitive to concentration.
• The superlinear current-voltage relationship at high concentrations suggests non-linear transport regimes.
• These findings inform the design and optimization of ion-selective membranes.