The ongoing progress of new and advanced ab initio methods greatly facilitates thermodynamic modeling of materials properties. Magnetic entropies being crucial for the description of, e.g., Fe-based alloys, can nowadays be modeled with an accuracy which sometimes succeeds the experimental one . More recently the methods have been advanced to account for the subtle interplay between spin and atomic degree of freedom by combining spin-space averaging procedures with Quantum Monte Carlo simulations . We discuss our developed methodologies focusing on the prototype example of BCC Fe where good agreement with high-quality phonon frequency measurements is found . We finally present how the methods can be extended towards Fe-based alloys as well as to properly account for longitudinal spin fluctuations (e.g. for FCC Ni).
 Körmann, Hickel, Neugebauer, COSSM, accepted.
 Körmann, Grabowski, Dutta, Hickel, Mauger, Fultz, Neugebauer, PRL (2014).