Prediction of entropy stabilized incommensurate phases in the system MoS 2 - MoTe 2 .

A first principles phase diagram calculation, that included van der Waals interactions, was performed for the 3D bulk system (1 - X ) · MoS 2 - ( X ) · MoTe 2 . Surprisingly, the predicted phase diagram has at least two ordered phases, at X ≈ 0:46, even though all calculated formation energies are positive; in a ground-state analysis that examined all configurations with 16 or fewer anion sites. The lower-temperature I -phase is predicted to transform to a higher-temperature I' -phase at T ≈ 500 K, and I' disorders at T ≈ 730 K. Both these transitions are predicted to be first-order, and there are broad two-phase fields on both sides of the ordered regions. Both the I - and I' -phases are predicted to be incommensurate , i.e., aperiodic : I -phase in three dimensions; and I' -phase in two dimensions.