Revealing the role of ripples in phonon modes for MoS2 and MoSe2: insights from molecular dynamics and machine learning

GBG de Souza and SB Hancock and DP Landau and Y Abate and R de Paiva and V Nascimento, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 27 (2025).

DOI: 10.1039/d5cp00163c

Interatomic potentials for single-layer MoS2 and MoSe2 were developed by training an artificial neural network with a reference data set generated using density functional theory. High accuracy was obtained for the phonon dispersion as well as a direct correspondence of the predicted Raman and infrared (IR) active modes (between 100 cm-1 and 600 cm-1) with molecular dynamics results. The ability to perform simulations with thousands of atoms allowed our system to accommodate spontaneous fluctuations in height and ripples propagating in the material. As a result of these ripples, our simulations suggest the existence of IR activity in the E ' and modes with inverted polarization, as well as the presence of IR activity at frequencies close to E '' and , which are generally considered IR-inactive. The rippling of the system is expected to be responsible for breaking the 3-fold rotational symmetry around the z-axis of the material, resulting in non-trivial IR modes.

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