Axial compression-induced post-buckling of nanotube films on copper nanopillars: a molecular dynamics study

Understanding the mechanical behavior of nanoscale films on substrates, particularly under compression, is crucial for NEMS and flexible electronics. While theoretical models describe film buckling, complexities arise at the nanoscale due to specific structures (like nanotubes) and substrate interactions, including plasticity, which are often simplified in continuum approaches. This study investigates the axial compression-induced post-buckling mechanisms of carbon nanotube (CNT) and boron nitride nanotube (BNNT) films interacting with copper nanopillars. Key questions addressed via molecular dynamics include how nanotube chirality and material stiffness influence buckling thresholds and post-buckling transitions (e.g., wrinkling, ridging, sagging), and how substrate size and deformability affect these processes. Initial findings reveal distinct behaviors linked to structure: armchair CNTs require higher buckling strains than zigzag CNTs, while stiffer BNNTs show delayed, abrupt transitions. Substrate plasticity significantly alters these deformation pathways compared to rigid substrate models.

Molecular dynamics (MD) simulations were conducted using LAMMPS, employing the Tersoff potential for CNT/BNNT covalent bonds and the Embedded Atom Model (EAM) for copper nanopillars. Lennard-Jones potentials modeled nanotube-substrate interactions. Simulations compared armchair/zigzag CNTs and armchair BNNTs on both fixed and deformable copper pillars of varying sizes at 0.1 K and 300 K. Axial compression was applied incrementally, followed by relaxation and unloading, to analyze buckling behavior, energy dissipation, and substrate deformation.