Semi-Automated Creation of Density Functional Tight Binding Models Through Leveraging Chebyshev Polynomial-based Force Fields

TL;DR

This paper introduces a semi-automated method for creating transferable Density Functional Tight Binding (DFTB) models using Chebyshev polynomial-based force fields, enabling efficient and accurate simulations across various conditions.

Contribution

The authors develop a rapid-screening workflow that leverages Chebyshev polynomial-based force fields to systematically generate and improve DFTB models for complex systems.

Findings

Model accurately predicts bulk and surface properties of TiH₂

Small training set suffices for broad thermodynamic conditions

Method is easy to implement and adaptable

Abstract

Density Functional Tight Binding (DFTB) is an attractive method for accelerated quantum simulations of condensed matter due to its enhanced computational efficiency over standard Density Functional Theory approaches. However, DFTB models can be challenging to determine for individual systems of interest, especially for metallic and interfacial systems where different bonding arrangements can lead to significant changes in electronic states. In this regard, we have created a rapid-screening approach for determining systematically improvable DFTB interaction potentials that can yield transferable models for a variety of conditions. Our method leverages a recent reactive molecular dynamics force field where many-body interactions are represented by linear combinations of Chebyshev polynomials. This allows for the efficient creation of multi-center representations with relative ease, requiring only a small investment in initial DFT calculations. We have focused our workflow on TiH$_2$ as a model system and show that a relatively small training set based on unit-cell sized calculations yields a model accurate for both bulk and surface properties. Our approach is easy to implement and can yield accurate DFTB models over a broad range of thermodynamic conditions, where physical and chemical properties can be difficult to interrogate directly and there is historically a significant reliance on theoretical approaches for interpretation and validation of experimental results.