Forces for Structural Optimizations in Correlated Materials within DFT+Embedded DMFT Functional Approach

TL;DR

This paper develops a method combining DFT and Embedded DMFT to efficiently compute forces for structural optimization in correlated materials, demonstrating its effectiveness on FeSe superconductor.

Contribution

It introduces a force calculation within DFT+Embedded DMFT that leverages quantum Monte Carlo noise cancellation for efficient structural optimization.

Findings

Strengthening of fluctuating moments increases anion height in FeSe.

The method achieves efficient structural optimization with reduced noise.

Results show large effective mass and orbital differentiation in FeSe.

Abstract

We implemented the derivative of the free energy functional with respect to the atom displacements, so called force, within the combination of Density Functional Theory and the Embedded Dynamical Mean Field Theory. We show that in combination with the numerically exact quantum Monte Carlo (MC) impurity solver, the MC noise cancels to a great extend, so that the method can be used very efficiently for structural optimization of correlated electron materials. As an application of the method, we show how strengthening of the fluctuating moment in FeSe superconductor leads to a substantial increase of the anion height, and consequently to a very large effective mass, and also strong orbital differentiation.