Abhiram Bindu Ramanathan, Ph.D.

Molybdenum disulfide (MoS2) is recognized for its mechanical robustness and exceptional lubricity under extreme conditions. However, its fracture behavior remains relatively unexplored, particularly across different crystalline configurations. We perform reactive molecular dynamics simulations to investigate the role of crystallinity on the fracture properties and behavior of MoS2. In a departure from prior studies focused on specific crystal orientations, we examine a spectrum of crystallinity, ranging from perfect crystal to polycrystalline to amorphous structures. Fracture properties are measured using the J-integral, ultimate strain, and brittleness index. Our results indicate that the presence of grain boundaries and amorphous regions within polycrystalline MoS2 enhances ductility and fracture toughness. However, at high degrees of crystallinity, grain boundaries dominate and act as a potential regions of defect, promoting crack propagation. Through an analysis of grain boundary interactions and atomic strain profiles, we elucidate critical insights into the mechanisms driving the observed variations in fracture properties. This study highlights the potential for tuning MoS2 crystallinity to optimize its fracture toughness, advancing its application in challenging engineering environments.