Atomistic Investigation of Kink Dynamics in Cyclotetramethylene‐tetranitramine ( β‐ HMX)

ABSTRACT Cyclotetramethylene‐tetranitramine ( β‐ HMX) is an anisotropic molecular crystal, which has extensive applications as secondary explosives. Understanding the dislocation movement in β‐ HMX is fundamental in projecting plastic deformation and mechanical behavior in continuum scales. While dislocation mobility in β‐ HMX has been investigated extensively, kink‐mediated dislocation motion is yet to be explored. Herein, we examine kink motion in two of the glissile slip systems of β‐ HMX: (011)[100]edge and (101)[010]edge. We have observed that the kinks in both systems initially split into dislocation partials. In (011)[100]edge system, during the kink motion the partials combine to form full kink monomers and propagate, whereas in (101)[010]edge system, the kink propagation happens through the motion of the dislocation partials. Our analysis reveals that the kinks can migrate along the dislocation line at shear stresses below the Peierls‐Nabarro stress for both systems; however, the order of magnitude of the stress remains the same. As the kink monomers move laterally in opposite directions, it facilitates the crossing of the entire dislocation over the lattice barrier. This result establishes kink motion as a viable mechanism for plastic deformation, emphasizing its addition to simulation models of explosive materials for understanding mechanical behavior.