  In this work we establish an approach to model miscibility gaps of alloys
using statistical physics, lattice dynamics from first-principles calculations.
We carefully calculate the entropy to include all processes introducing
disorder to the system, i.e., combining the electronic, phononic, and
configuration entropies. Furthermore we present our algorithm for generating
Special Quasirandom Structures (SQS). We model the miscibility gap in tungsten
- chromium and tungsten - molybdenum systems, obtaining the agreement with the
experimental data. Furthermore, we propose an enhancement for the
tungsten-chromium W$_{70}$Cr$_{30}$ alloy with tantalum and hafnium, leading to
the modified stabilization temperatures $T_S$, where the solid solution is
miscible.
