Abstract
Asymmetric Janus transition metal dichalcogenide MoSSe is a promising catalytic material due to the intrinsic in-plane dipole of its opposite faces. The atomic description of the structures observed by experimental techniques is relevant to tuning and optimizing its surface reaction processes. Furthermore, the experimentally observed triangular morphologies in MoSSe suggest that an analysis of the chemical environment of its edges is vital to understand its reactivity. Here we analyze the size-shape stability among different triangular structures-quantum- dots proposed from the ideal S(-1010) and Mo(10-10) terminations. Our stability analysis evidenced that the S–Se termination is more stable than Mo; moreover, as the size of the quantum dot increases, its stability increases as well. Besides, a trend is observed, with the appearance of elongated Mo-S/Se bonds at symmetric positions of the edges. Tersoff–Hamann scanning tunneling microscopy images for both faces of the stablest models are presented. Electrostatic potential isosurfaces denote that the basal plane on the S face of both configurations remains the region with more electron density concentration. These results point toward the differentiated activity over both faces. Finally, our study denotes the exact atomic arrangement on the edges of MoSSe quantum dots corresponding with the formation of S/Se dimers who decorates the edges and their role along with the faces as catalytic sites.
Highlights
Thermal equilibrium between the bulk, vacuum, and molecular structure has been considered to establish the following correlation among chemical potentia
Exchange-correlation energies were treated within the generalized gradient framework (GGA) with a Perdew-Burke-Ernzerhof (PBE) functional[40]
The force and energy criteria employed for the structural optimization were achieved when differences were lower than 0.01 eV/Å and 1 × 10−4 eV
Summary
Thermal equilibrium between the bulk, vacuum, and molecular structure has been considered to establish the following correlation among chemical potentia. The stability of MoSSe quantum dots as a function of their size and termination has been analyzed by spinpolarized total-energy calculations through density functional theory as implemented in the Vienna ab initio simulation package[35,36,37,38,39]. The electronic states of the pseudo-wave function were modeled with an expansion of plane waves with an optimized cutoff energy of 500 eV.
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