Abstract
In recent years, the Janus monolayers have attracted tremendous attention due to their unique asymmetric structures and intriguing physical properties. However, the thermal stability of such two-dimensional systems is less known. Using the Janus monolayers SnXY (X, Y = O, S, Se) as a prototypical class of examples, we investigate their structure evolutions by performing ab-initio molecular dynamics (AIMD) simulations at a series of temperatures. It is found that the system with higher thermal stability exhibits a smaller difference in the bond length of Sn–X and Sn–Y, which is consistent with the orders obtained by comparing their electron localization functions (ELFs) and atomic displacement parameters (ADPs). In principle, the different thermal stability of these Janus structures is governed by their distinct anharmonicity. On top of these results, we propose a simple rule to quickly predict the maximum temperature up to which the Janus monolayer can stably exist, where the only input is the ADP calculated by the second-order interatomic force constants rather than time-consuming AIMD simulations at various temperatures. Furthermore, our rule can be generalized to predict the thermal stability of other Janus monolayers and similar structures.
Highlights
SnXY (X, Y = O, S, Se) as a prototypical class of examples, we focus on their thermal stability by performing ab-initio molecular dynamics (AIMD) simulations at a series of temperatures
The thermal stability of our Janus systems can be evaluated by performing AIMD simulations, which are implemented in the Vienna ab-initio Simulation Package (VASP) [28–30]
We demonstrated by AIMD simulations that the Janus monolayer SnXY
Summary
Academic Editors: Gang Zhang, During the past decades, graphene and other two-dimensional (2D) materials have attracted widespread attention from the science community [1–7]. In 2017, the Janus MoSSe was successfully fabricated from 2D transition metal dichalcogenide (TMD) MoS2 , where the. As various Janus structures have been recently proposed theoretically, it is natural to check their stability before any realistic application. First-principles calculations by Shi et al [15] demonstrated that the Janus monolayers MXY (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and X, Y = S, Se, Te) are mechanically stable. Inspired by the fabrication of the 2D TMD VSe2 , Zhang et al [16] predicted an energetically and dynamically stable Janus structure of VSSe, and further checked its thermal stability at room temperature. Peng et al [17] proposed a stable Janus monolayer PtSSe, which was later successfully prepared by Sant et al [18] via
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