First-Principles Nanocapacitor Simulations of the Optical Dielectric Constant in Water Ice

Area of Science:

• Condensed matter physics
• Materials science
• Computational chemistry

Background:

• Conventional capacitance measurements at the nanoscale are complicated by ambiguous charge partitioning between electrodes and dielectrics.
• This ambiguity affects the accurate determination of dielectric properties and introduces spurious interfacial effects.

Purpose of the Study:

• To develop a robust computational framework for accurately calculating nanocapacitor capacitance and dielectric response.
• To address the challenges of charge partitioning in nanoscale systems.
• To investigate the dielectric properties of subnanometer dielectrics, specifically crystalline ice, under bias.

Main Methods:

• Combined density functional theory (DFT) and nonequilibrium Green's function (NEGF) framework.
• Development of a novel charge-separation protocol to resolve electrode and dielectric contributions.
• Analysis of crystalline ice as a model subnanometer dielectric material.

Main Results:

• The new framework accurately computes capacitance and extracts dielectric response, overcoming ill-posed charge partitioning issues.
• The robust charge-separation protocol yields unique capacitance-derived polarizability and dielectric constants for crystalline ice.
• Demonstrated that nanoscale confinement does not alter the intrinsic electronic response or proton order insensitivity of crystalline ice.

Conclusions:

• The developed DFT-NEGF framework provides a rigorous approach for interpreting capacitance measurements in low-dimensional dielectric materials.
• This work establishes a foundation for understanding dielectric behavior in nanoscale devices.
• Highlights the importance of accurate charge partitioning for reliable nanoscale dielectric characterization.