Prediction of the Kinetics of Structural Phase Changes in Two-dimensional MoS2 at the Semiconducting to Metallic Phase Boundary

Aditi Krishnapriyan, Stanford University

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Utilizing the phase transition between the metallic 1T or 1T' and semiconducting 2H structures in two-dimensional materials may provide exciting new opportunities for energy-efficient applications, such as in electronic and optical devices. However, little is known about the mechanisms and kinetics of these phase changes. Using computational geometry algorithms, density functional theory (DFT) and the Wulff construction method, we propose a novel method to determine the minimum energy nanoparticle and the resulting nucleation barrier of the 1T or 1T' metallic phases in a 2H semiconducting lattice; we verify these results using DFT. We identify multiple zigzag interfaces at the metallic-to-semiconducting phase boundary and predict that the lowest energy nanoparticle shape of 1T in a 2H lattice is kite-shaped while for 1T' in a 2H lattice it is triangular. We also show that due to the nature of the system's geometric constraints, the individual interface energies between phases are mathematically ill-defined and there are only certain allowed interface configurations. Finally, we discuss the nucleation barriers, critical nucleus size and approximate nucleation time. This work points to strategies for the engineering of kinetics in these phase-change materials. The information gleaned from this is applied to a tight-binding/machine learning model as training data.

Abstract Author(s): Aditi Krishnapriyan, Evan Reed