Ab initio studies of electronic and vibrational properties of transition metal dichalcogenides systems under hydrostatic pressure

We study from first principles (DFT) the electronic structure of MoTe₂ and WS₂ under hydrostatic pressure in comparison to photoreflectance spectra. The analysis based on pressure coefficients allowed for identification of several optical transitions in bulk and multilayer systems. The calculated pressure coefficients for K and H point transitions are in good agreement with the experimental values. [1]
Lattice dynamics of bulk HfS₂ and MoS₂ in comparison to high pressure Raman scattering measurements is studied. From the calculated phonon dispersions we derive linear pressure coefficients which are then compared to experimental data. DFT calculations were performed using various functionals, vdW corrections and lattice dynamics calculations methods. We find that GGA properly describes the high pressure lattice dynamics of these compounds when vdW interactions are taken into account. In contrast, we show that LDA, which is widely used to predict structural and vibrational properties at ambient conditions in 2D compounds, fails to reproduce the Raman modes evolution under compression. [2]

[1] J. Kopaczek, T. Wozniak, R. Kudrawiec, to be submitted
[2] J. Ibanez, T. Wozniak, F. Dybala, R. Oliva, S. Hernandez & R. Kudrawiec, Sci. Rep. (2018) 8:12757