## Abstract

First principles phase diagram calculations, that included van der Waals interactions, were performed for the bulk transition metal dichalcogenide system (1−X)·WS_{2}−(X)·WTe_{2}. 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.

Original language | English |
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Pages (from-to) | 142-147 |

Journal | Calphad: Computer Coupling of Phase Diagrams and Thermochemistry |

Volume | 63 |

DOIs | |

Publication status | Published - 2018 |

### Bibliographical note

Accepted Author Manuscript## Keywords

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

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