  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.
