Isostructural transitions in layered MX2 compounds are governed by competing van der Waals (vdW) and Coulomb interactions. While an isostructural transition (at P∼ 20 GPa) has been observed before metallization in MoS2 when subjected to pressure, it is surprisingly missing in layered MoSe2 and MoTe2. Using synchrotron x-ray diffraction and Raman spectroscopic measurements of structural and vibrational properties of layered MoSSe crystals subjected to pressures up to 30 GPa and first-principles density functional theoretical analysis, we demonstrate a layer sliding isostructural transition from its 2H′c structure (space group P63mc) to a mixed-phase of 2H′a+2H′c at P∼ 10.8 GPa, marked by discontinuity in lattice parameters, pressure coefficients of Raman modes, and accompanying changes in electronic structure.
(Achintya Bera, Y. A. Sorb, Ramesh Naidu Jenjeti, D. V. S. Muthu, S. Sampath, Chandrabhas Narayana, U. V. Waghmare, and A. K. Sood are other authors of this paper.)