We report high pressure x-ray diffraction and systematic Raman measurements on a ReS 2 sample, which is mechanically exfoliated from a single crystal. A few new Bragg peaks are observed to emerge above 6 GPa indicating a structural transition from distorted 1T to distorted 1T 0 in a triclinic structure. The same is corroborated by the appearance of new Raman modes in the same pressure range. Softening of the Raman modes corresponding to Re atom vibrations is observed in the distorted 1T 0 phase in the pressure range of 15-25 GPa. In the same pressure range, the anomalous change in the volume is found to be induced by the lattice expansion. The volume expansion is related to the sliding of layers leading to octahedral distortion and an increase in octahedral volume. The sample is found to be very incompressible above 25 GPa with respect to below 15 GPa data. The same is also reflected in the Raman mode shifts with pressure.

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Detailed high pressure Resonance Raman (RR) Spectroscopy and x-ray diffraction (XRD) studies are carried out on 3-4 layered MoSe 2 obtained by liquid exfoliation. Analysis of ambient XRD pattern and RR spectra indicate the presence of a triclinic phase along with its parent hexagonal phase. Slope change in the linear behavior of reduced pressure (H) with respect to Eulerian strain ( f E ) is observed at about 13 GPa in hexagonal phase and at about 17 GPa for the triclinic phase. High pressure Raman measurements using two different pressure transmitting media (PTM) show three linear pressure regions, separated by pressure values around which anomalies in the structure are observed. A broad minimum in the FWHM values of E g 2 1 mode at about 10-12 GPa indicate to an electron-phonon coupling. Above 33 GPa the sample completely gets converted to the triclinic structure, which indicates the importance of strain in structural as well as electronic properties of two dimensional materials.

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We report high pressure X-ray diffraction and a detailed systematic Raman measurements on ReS 2 sample, which is mechanically exfoliated from a single crystal. A few new Bragg peaks are observed to emerge above 6 GPa indicating a structural transition from distorted 1T to distorted 1T ′ in triclinic structure. The same is corroborated by appearance of new Raman modes in the same pressure range. Softening of the Raman modes corresponding to Re atom vibrations are observed in the distorted 1T ′ phase in the pressure range 15-25 GPa. In the same pressure range the anomalous change in the volume is found to be induced by the lattice expansion. The volume expansion is related to the sliding of layers leading to octahedral distortion and increase in octahedral volume.The sample is found to be much incompressible above 25 GPa with respect to below 15 GPa data.The same is also reflected in the Raman mode shifts with pressure.