Kolmogorov–Crespi Potential For Multilayer Transition-Metal Dichalcogenides: Capturing Structural Transformations in Moiré Superlattices

Abstract

We develop parameters for the interlayer Kolmogorov-Crespi (KC) potential to study structural features of four transition metal dichalcogenides (TMDs): MoS 2 , WS 2 , MoSe 2 and WSe 2 . We also propose a mixing rule to extend the parameters to their heterostructures. Moiré superlattices of twisted bilayer TMDs have been recently shown to host shear solitons, topological point defects and ultraflatbands close to the valence band edge. Performing structural relaxations at the DFT level is a major bottleneck in the study of these systems. We show that the parametrized KC potential can be used to obtain atomic relaxations in good agreement with DFT relaxations. Furthermore, the moiré superlattices relaxed using DFT and the proposed forcefield yield very similar electronic band structures.

Phonons in twisted transition-metal dichalcogenide bilayers: Ultrasoft phasons and a transition from a superlubric to a pinned phase

“…All the parameters reported in Ref. [32] should produce similar results. We use modified PHONOPY [44,45] code to compute the zero-temperature vibrational spectra of the relaxed TBL MoS 2 .…”

“…We use the TWISTER code [34] to create the MSL of bilayer MoS 2 with several commensurate twist angles 1 • < θ < 59 • . The rigidly twisted structures are relaxed using LAMMPS [38][39][40] with the Stillinger-Weber and Kolmogorov-Crespi potentials to capture the intralayer [41,42] and interlayer interactions of TBL MoS 2 [32,43], respectively. The Kolmogorov-Crespi parameters used in our calculations correctly reproduce the interlayer binding energy landscape, obtained using density functional theory.…”

“…Since the low-frequency modes are solely determined by interlayer coupling and are accessible in Raman measurements, they provide a direct nondestructive probe of the interlayer interaction [27][28][29][30]. The existing theoretical reports on the evolution of vibrational modes in twisted structures are restricted to large twist angles and use the Lennard-Jones potential [31] to describe the interlayer interaction, which is insufficient for capturing the stackingdependent energetics [32]. Although existing experimental studies [29,30,33] have explored small twist angles, they can only probe Raman active modes with frequencies greater than 10 cm −1 .…”

Multiscale computational understanding and growth of 2D materials: a review

“…While being used to capture vdW interactions, a limitation of the pairwise interaction is the inability to capture frictional processes, such as the sliding of atomic layers. Different corrections have been proposed to overcome this shortcoming [68][69][70] . The two potential parameters ϵ and σ can be determined by using one energy quantity like the binding energy and a structural quantity like the density.…”

Tuning Valleys and Wave Functions of van der Waals Heterostructures by Varying the Number of Layers: A First‐Principles Study

“…2D transition-metal dichalcogenides (TMDCs) have been intensively studied in the past decade, not only as single layers, [1,2] but, more recently, also as bilayer (2L) van der Waals heterostructures (vdW HS), [3][4][5][6][7][8][9][10][11] where two different monolayers (1L) are vertically stacked, forming ubiquitous moiré patterns, due to the lattice mismatch and twist angle between individual layers. [12][13][14] Such vdW HS offer bandgaps smaller than these of parental single layers and interlayer excitons, which are longer-lived, because…”