Free energy from stationary implementation of the DFT+DMFT functional

TL;DR

This paper introduces a novel stationary functional approach combining DFT and DMFT for accurate free energy calculations, enabling precise structural predictions and resolving longstanding debates in phase transition mechanisms.

Contribution

It is the first implementation of a stationary DFT+DMFT functional for free energy calculations and structural relaxations, reducing errors and improving accuracy in correlated materials.

Findings

Accurately predicts lattice constants for SrVO3, FeO, and Cerium.

Successfully models the alpha-gamma transition in Cerium.

Resolves controversy over the transition's driving mechanism.

Abstract

The stationary functional of the all-electron density functional plus dynamical mean field theory (DFT+DMFT) formalism to perform free energy calculations and structural relaxations is implemented for the first time. Here, the first order error in the density leads to a much smaller, second order error in the free energy. The method is applied to several well known correlated materials; metallic SrVO$_3$, Mott insulating FeO, and elemental Cerium, to show that it predicts the lattice constants with very high accuracy. In Cerium, we show that our method predicts the iso-structural transition between the $\alpha$ and $\gamma$ phases, and resolve the long standing controversy in the driving mechanism of this transition.