Long-wavelength TDDFT Enables Accurate Conductivity Calculations for Heterogeneous Systems

Understanding how materials interact with electromagnetic fields is fundamental to many technologies, and scientists continually refine methods for accurately predicting this behaviour. Christian Tantardini from King Fahd University of Petroleum and Minerals, Quentin Pitteloud from UiT The Arctic University of Norway, Boris Yakobson from Rice University, and Martin Andersson from King Fahd University of Petroleum and Minerals, present a new theoretical framework that seamlessly connects calculations of molecular polarizability with the prediction of electrical conductivity in complex, heterogeneous materials. This achievement overcomes a long-standing challenge in accurately modelling materials with varying compositions and structures, offering a unified approach applicable from radio frequencies to ultraviolet light. The resulting method promises more reliable predictions of crucial material properties, including heating efficiency, penetration depth, and interfacial behaviour, with potential applications ranging from dielectric logging to the development of advanced digital twins for multiphysics simulations.

Electromagnetic response is commonly computed using two distinct approaches: length-gauge molecular polarizabilities and velocity-gauge (Kubo) conductivities for periodic solids. This work introduces a compact, gauge-invariant bridge that utilises the same microscopic inputs, transition dipoles and interaction kernels, for calculations spanning molecules, crystals and heterogeneous media. The method incorporates explicit SI prefactors and fine-structure scaling, ensuring accuracy and consistency across different systems. Handling the long-wavelength limit involves a reduced dielectric matrix that accurately retains local-field mixing, while interfaces and two-dimensional layers are treated with appropriate boundary conditions.

Many-Body Effects and Optical Response Calculations

This document details a theoretical framework and implementation for calculating optical and electronic properties of materials, with a particular emphasis on accurately handling many-body effects and interfaces. The authors aim to provide a robust and consistent method for predicting material behavior. A key focus is on correctly treating the response of materials to electromagnetic radiation and how electrons interact within the material. The framework allows for the calculation of electronic band structure and accurately models interfaces, crucial for understanding heterostructures and devices. The authors emphasize the importance of including non-local effects and use sum rules to ensure the accuracy and consistency of their calculations.

Molecular Polarizabilities Predict Macroscopic Material Response

Scientists have developed a comprehensive framework for calculating the electromagnetic response of materials, extending from individual molecules to complex solids and heterogeneous media. This work establishes a robust connection between molecular polarizabilities and the conductivities of periodic materials, ensuring unit consistency across different scales. The method accurately accounts for local-field mixing, interfaces, and two-dimensional layers, avoiding approximations common in ultrathin film treatments. Numerical tests confirm the framework’s accuracy through verification of length-velocity equivalence and saturation of optical f-sum rules. The researchers implemented a finite-temperature formulation, enabling calculations of material properties at non-zero temperatures, and accurately calculate the extinction cross-section, a key parameter for understanding light absorption and scattering.

Unified Framework for Electromagnetic Response Calculations

This work presents a comprehensive framework bridging electromagnetic response calculations across molecular, crystalline, and heterogeneous materials. Researchers have developed a gauge-invariant method that consistently connects microscopic properties, such as transition dipoles and interaction kernels, to macroscopic observables, ensuring accuracy from radio frequencies to ultraviolet wavelengths. The approach accurately describes dielectric properties, interfacial effects in thin films and two-dimensional materials, and adsorption metrics. The team demonstrated the equivalence of length and velocity gauges in their calculations and successfully implemented a method for handling finite temperatures within their simulations. They also established clear connections between fundamental constants and material-specific responses, facilitating comparisons between different systems.