Two-dimensional (2D) transition metal dichalcogenides (TMDs), like MoS2, have unique electronic and optical properties, which can further be tuned using ion bombardment and post-synthesis ion-beam mediated methods combined with exposure of the irradiated sample to precursor gases. The optimization of these techniques requires a complete understanding of the response of 2D TMDs to ion irradiation, which is affected by the reduced dimensionality of the system. By combining analytical potential molecular dynamics with first-principles calculations, we study the production of defects in free-standing MoS2 sheets under noble gas ion irradiation for a wide range of ion energies when nuclear stopping dominates, and assess the probabilities for different defects to appear. We show that depending on the incident angle, ion type and energy, sulfur atoms can be sputtered away predominantly from the top or bottom layers, creating unique opportunities for engineering mixed MoSX compounds where X are chemical elements from group V or VII. We study the electronic structure of such systems, demonstrate that they can be metals, and finally discuss how metal/semiconductor/metal junctions, which exhibit negative differential resistance, can be designed using focused ion beams combined with the exposure of the system to fluorine.

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In the present work, nanoindentation on the basal surface of a crystalline molybdenum disulfide (MoS2) thin film is investigated by molecular statics (MS) calculations. A previously parameterized interatomic potential combining the reactive empirical bond-order and Lennard-Jones potentials is implemented into the LAMMPS molecular simulation package and refined for improved prediction of the mechanical properties of MoS2 at athermal conditions. Nanoindentation simulations are performed using three indenter sizes with specific focus on the incipient plastic deformation event within the MoS2single crystal. MS calculations show that a local phase transformation occurs beneath the indenter at plastic yield without the presence of broken Mo–S bonds. The structural characteristics of the phase transformation are captured using a slip vector analysis. The nanoindentation simulations provide insight into the mechanical response of MoS2 during contact deformation characteristic of both synthesis and application for better design of MoS2 nanoparticle lubricants.

Electron and x-ray diffraction are well-established experimental methods used to explore the atomic scale structure of materials. In this work, a computational method is implemented to produce virtual electron and x-ray diffraction patterns directly from atomistic simulations without a priori knowledge of the unit cell. This method is applied to study the structure of [0 1 0] symmetric tilt low-angle and large-angle grain boundaries in Ni. Virtual electron diffraction patterns and x-ray diffraction 2θ line profiles show that this method can distinguish between low-angle grain boundaries with different misorientations and between low-angle boundaries with the same misorientation but different dislocation configurations. For large-angle 5 (2 1 0), 29 (5 2 0) and 5 (3 1 0) coincident site lattice [0 1 0] symmetric tilt grain boundaries, virtual diffraction methods can identify the misorientation of the grain boundary and show subtle differences between grain boundaries in the x-ray 2θ line profiles. A thorough analysis of the effects of simulation size on the relrod structure in the electron diffraction patterns is presented.

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