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Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster Session I

HL 13.2: Poster

Monday, March 12, 2018, 17:30–19:30, Poster B

First Principles Phase Diagram Calculations for the 2D TMD systems MoS2MoTe2  and WS2WTe2. — •Benjamin Burton — Materials Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, USA

First Principles Phase Diagram Calculations were performed for the 2D Transition Metal Dichalcogenide Systems MoS2MoTe2  and WS2WTe2. These FPPD calculations were performed with the ATAT system using VASP calculated formation energies for MS2−2xTe2x  supercells (M=Mo or W) as input. For both of these systems, very surprising results were obtained: (1) although all calculated formation energies for systems with 16 or fewer anion sites were positive, suggesting a miscibility gap, entropy stabilized intermediate phases were predicted in Mo(S,Te)2; (2) although one expects immiscibility to be greater on the S-rich sides of these diagrams (because S2−  is a smaller ion than Te2−) it is much greater on the Te-rich sides.This surprising asymmetry is understood as reflecting a preponderance of lower-energy metastable ordered states on the S-rich sides of the systems.

The calculated phase diagrams are for bulk systems, but results for monolayers of Mo(S,Te)2 on a saphire substrate [Al-terminated, (0001) face] will also be discussed.

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