Temperature-dependent Raman spectra of 2H-MoS2 from Machine Learning-driven statistical sampling

Abstract

Molybdenum sulfides are in the spotlight of materials science thanks to their interesting properties for applications in optoelectronics, nanocomposites, lubricants, and catalysis. The structural characterization of Molybdenum sulfides is a crucial step to understand and tune their properties. Vibrational techniques, such as infrared and Raman spectroscopy, can directly link to structural features, but the experimental literature suffers from large variability. Theoretical calculations are a powerful tool complementing and explaining empirical measurements. The reliability of first-principles calculation depends on the level of approximation made, taking into account disorder, doping, or temperature to yield a good description of the phonon statistics and related measurable quantities, such as the infrared and Raman peaks. In this study we calculate the Raman spectrum of crystalline 2H-MoS2, including broadening and shifts due to thermal and anharmonic effects. Our results demonstrate excellent agreement with experimental measurements; notably, the calculated temperature trends in frequencies and linewidths align with empirical observations. These findings establish a robust computational framework, paving the way for similar studies on amorphous Molybdenum sulfides.

Figures (7)

• Figure 1: 2H-MoS$_2$ lattice parameters vs temperature from our study and experimental work by El-Mahalawy et al. El-mahalawy1976 and Murray et al. Murray1979. The data was fit to a linear function in T (dashed lines), and $\chi$ are the angular coefficients.
• Figure 2: Phonon bands of MoS$_2$ from 100 to 700 K calculated with MD-TDEP.
• Figure 3: Calculated phonon bands at 300 K with stochastic and MD sampling, and experimental data from Ref. Tornatzky2019.
• Figure 4: Position and FWHM of the peaks in MoS$_2$ spectral function vs temperature from theoretical calculations (with MD and stochastic sampling) and experimental Raman spectra from Cao and Chen Cao2019 vs temperature.
• Figure 5: R$^2$ of the TDEP fit of IFCs at the second and third order vs temperature with the MD and stochastic sampling.