Collapse modes in SC and BCC 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 provide important insights on the origins of mechanical behavior of atomic systems, while the elastic spheres model used in our work can become a useful paradigm, expanding the capabilities of a hard sphere model widely used in many branches of science.