Unraveling Mn intercalation and diffusion in NbSe$_2$ bilayers through DFTB simulations

TL;DR

This study uses DFTB simulations to explore how manganese atoms intercalate and diffuse within NbSe₂ bilayers, revealing preferred stable positions, energy barriers, and concentration-dependent behaviors relevant for 2D material applications.

Contribution

It provides new atomic-scale insights into Mn intercalation and diffusion mechanisms in NbSe₂ bilayers using DFTB simulations, which were not previously detailed.

Findings

Mn prefers intercalated and embedded positions over surface adsorption.

Energy barrier for Mn migration into the interlayer is 0.68 eV.

Intercalation behavior depends on Mn concentration and density.

Abstract

Understanding transition metal atoms' intercalation and diffusion behavior in two-dimensional (2D) materials is essential for advancing their potential in spintronics and other emerging technologies. In this study, we used density functional tight binding (DFTB) simulations to investigate the atomic-scale mechanisms of manganese (Mn) intercalation into NbSe$_2$ bilayers. Our results show that Mn prefers intercalated and embedded positions rather than surface adsorption, as cohesive energy calculations indicate enhanced stability in these configurations. Nudged elastic band (NEB) calculations revealed an energy barrier of 0.68 eV for the migration of Mn into the interlayer, comparable to other substrates, suggesting accessible diffusion pathways. Molecular dynamics (MD) simulations further demonstrated an intercalation concentration-dependent behavior. Mn atoms initially adsorb on the surface and gradually diffuse inward, resulting in an effective intercalation at higher Mn densities before clustering effects emerge. These results provide helpful insights into the diffusion pathways and stability of Mn atoms within NbSe$_2$ bilayers, consistent with experimental observations and offering a deeper understanding of heteroatom intercalation mechanisms in transition metal dichalcogenides.