First principles phase diagram calculation for the 2D TMD system WS₂−WTe₂

First principles phase diagram calculation for the 2D TMD system WS₂−WTe₂

Burton, B. P. (National Institute of Standards and Technology)
Sluiter, M.H.F. (TU Delft (OLD) MSE-7)

2018

First principles phase diagram calculations, that included van der Waals interactions, were performed for the bulk transition metal dichalcogenide system (1−X)·WS₂−(X)·WTe₂. To obtain a converged phase diagram, a series of cluster expansion calculations were performed with increasing numbers of structural energies, (N_str) up to N_str=435, used to fit the cluster expansion Hamiltonian. All calculated formation energies are positive and all ground-state analyses predict that formation energies for supercells with 16 or fewer anion sites are positive; but when 150⪅N_str⪅376, false ordered ground-states are predicted. With N_str≥399, only a miscibility gap is predicted, but one with dramatic asymmetry opposite to what one expects from size-effect considerations; i.e. the calculations predict more solubility on the small-ion S-rich side of the diagram and less on the large-ion Te-rich side. This occurs because S-rich low-energy metastable ordered configurations have lower energies than their Te-rich counterparts which suggests that elastic relaxation effects are not dominant for the shape of the miscibility gap.

First principles
Phase diagram calculation
TMD
Transition metal dichalcogenide
Van der Waals
WS2−WTe2

http://resolver.tudelft.nl/uuid:0d33360e-69f5-455e-9dcf-431b3b51ad6a

https://doi.org/10.1016/j.calphad.2018.08.001

2020-09-27

0364-5916

CALPHAD: the international research journal for calculation of phase diagrams, 63, 142-147

Accepted Author Manuscript

Institutional Repository

journal article

© 2018 B. P. Burton, M.H.F. Sluiter