Atomistic observation of the collision and migration of Li on MoSe₂ and WS₂ surfaces through ab initio molecular dynamics

Abstract

We present in this study a theoretical investigation of the collision of Li with the MX surface (MoSe or WS) by employing the Born-Oppenheimer molecular dynamics (MD) approach. In each trajectory, atomic Li is fired toward the two-dimensional monolayer with an inletting kinetic energy of 0.2 eV or 2.0 eV and a chosen striking angle. In total, 84 MD trajectories are analyzed. We observe that Li has a high tendency to migrate on WS in most investigated cases (20/21 cases at 0.2 eV inletting kinetic energy and 21/21 cases at 2.0 eV inletting kinetic energy), while the migration probability on MoSe is much lower (only 5/21 cases with the inletting kinetic energy of 0.2 eV and 15/21 cases with the inletting kinetic energy of 2.0 eV). Interestingly, our finding shows that the migration probability does not depend on the binding energies of Li-MoSe (1.61 eV) and Li-WS (1.77 eV), but it is in good agreement with the nudged-elastic-band prediction of migration barriers. In fact, it is the intensity of elastic vibration of the transition metal dichalcogenide layer that plays a very significant role in the migration of Li. During the collision process, Li is able to absorb energy from the layer vibration to jump out from one X-X-X trap to another. Consequently, with the assistance from intensive vibration of WS, Li would possess higher migration probability on the layer surface. Finally, electronic structure analysis on various interacting Li-MX configurations is performed. From Bader charge estimation, we observe that WS tends to establish more charge transferability with Li. Moreover, when Li approaches closer to the S/Se layer, the hybridization of Li-2s and Mo-4d (or W-5d) orbitals results in a magnetic moment (up to ∼1 μ).

Induced Magnetism of the MoS2 Monolayer during the Transition Metal (Fe/Ni) Bombardment Process: A Nonadiabatic Ab Initio Collision Dynamics Investigation

“…The in-plane lattice parameter for the supercell is 9.59 Å, while the vacuum thickness of 15 Å is adopted to minimize the spurious interaction between neighboring slabs in the z direction. In previous studies, , the variation of lattice constant was observed to change insignificantly during the collision process. Thus, the defined lattice parameter is held constant during the entire MD investigation to reduce computational effort.…”

“…This shows an enormous attraction from the TMDC layer that pulls the metal atom strongly. In the previous studies, the MoS 2 vibration is observed to play an important role in the movement of the metal atom toward MoS 2 . , The up and down motion of MoS 2 is due to internal vibration, which can be regarded as the “breathing” behavior, which attracts the metal atom and partially evokes the enhancement of kinetic energy. At an initial temperature of 300 K, the approximate period for thermal vibration of MoS 2 is about 28 fs.…”

“…The MD trajectories are simulated by employing our MD external driver with the implemented velocity Verlet algorithm, which was described in the previous studies, ,, to investigate the collision process. A fixed time step of 10 time units in the Hartree atomic unit (0.24 fs) is used to integrate the equations of motion.…”