TY - JOUR

T1 - First principles phase diagram calculation for the 2D TMD system WS2−WTe2

AU - Burton, B. P.

AU - Sluiter, M. H.F.

N1 - Accepted Author Manuscript

PY - 2018

Y1 - 2018

N2 - 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.

AB - 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.

KW - First principles

KW - Phase diagram calculation

KW - TMD

KW - Transition metal dichalcogenide

KW - Van der Waals

KW - WS2−WTe2

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

UR - http://www.scopus.com/inward/record.url?scp=85054012661&partnerID=8YFLogxK

U2 - 10.1016/j.calphad.2018.08.001

DO - 10.1016/j.calphad.2018.08.001

M3 - Article

AN - SCOPUS:85054012661

VL - 63

SP - 142

EP - 147

JO - CALPHAD: the international research journal for calculation of phase diagrams

JF - CALPHAD: the international research journal for calculation of phase diagrams

SN - 0364-5916

ER -