Collapse modes in simple cubic and body-centered cubic arrangements of elastic beads

Collapse modes in compressed simple cubic (SC) and body-centered cubic (BCC) periodic arrangements of elastic frictionless beads were studied numerically using the discrete element method. Under pure hydrostatic compression, the SC arrangement tends to transform into a defective hexagonal close-packed or amorphous structure. The BCC assembly exhibits several modes of collapse, one of which, identified as cI16 structure, is consistent with the behavior of BCC metals Li and Na under high pressure. The presence of a deviatoric stress leads to the transformation of the BCC structure into face-centered cubic (FCC) one via the Bain path. The observed effects expand the knowledge on possible packings of soft elastic spheres and transformations between them, while providing an unexpected link with the mechanical behavior of certain atomic systems.