Pressure-driven polymerization and low-symmetry phase transitions in carbon nanotubes

Abstract Carbon nanotubes exhibit remarkable mechanical and electronic properties, and understanding their response to high pressure is essential for advancing applications in microelectronics, sensors, and high-strength materials. In this work, the structural evolution of armchair and zigzag nanotubes—(7,7), (8,8), (11,0), and (12,0)—is investigated using first-principles calculations. Under compression, the nanotubes transform into oval, peanut, and elliptical geometries, with clear evidence of inter-tube polymerization and stacking. Flattened 3D-linked structures and the formation of graphene bilayers are also evident. Compression–decompression cycles further generate new metastable configurations. Structural collapse occurs around 10 GPa for (11,0), and pressure induces significant electronic modifications where the semiconducting (11,0) becomes metallic. Analysis of the band structures and projected density of states clarifies the mechanisms behind these transitions. Overall, the results show that high pressure provides an effective pathway to tune both structural and electronic properties of carbon nanotubes, highlighting their potential for future technological applications.