  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.
