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

B. P. Burton, M. H.F. Sluiter

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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, (Nstr) up to Nstr=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⪅Nstr⪅376, false ordered ground-states are predicted. With Nstr≥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.

Original languageEnglish
Pages (from-to)142-147
JournalCalphad: Computer Coupling of Phase Diagrams and Thermochemistry
Publication statusPublished - 2018

Bibliographical note

Accepted Author Manuscript


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


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