Embedded fragment stochastic density functional theory

TL;DR

This paper introduces an improved stochastic DFT method that accurately computes the electronic density of large systems by embedding small fragment densities, overcoming convergence issues and charge fluctuation problems.

Contribution

The paper presents a novel embedding approach in stochastic DFT that enhances accuracy and convergence for weakly coupled subsystems.

Findings

Accurately describes density of states and total energy with fewer stochastic orbitals.

Successfully applied to fullerene dimers and water clusters.

Overcomes convergence and charge fluctuation issues of previous stochastic DFT methods.

Abstract

We develop a method in which the electronic densities of small fragments determined by Kohn-Sham density functional theory (DFT) are embedded using stochastic DFT to form the exact density of the full system. The new method preserves the scaling and the simplicity of the stochastic DFT but cures the slow convergence that occurs when weakly coupled subsystems are treated. It overcomes the spurious charge fluctuations that impair the applications of the original stochastic DFT approach. We demonstrate the new approach on a fullerene dimer and on clusters of water molecules and show that the density of states and the total energy can be accurately described with a relatively small number of stochastic orbitals.