Mechanistic aspects and atomic-level consequences of elastic instabilities in homogeneous crystals

Elastic stability criteria, derived for a homogenous lattice under arbitrary external load, provide an upper bound on the critical stress or strain which a crystalline solid can withstand. Since the onset of a structural instability is load dependent, the corresponding theoretical strength can be given similar interpretation. When combined with molecular dynamics simulation, such results allow a systematic discussion of competing structural transitions, as illustrated here in a case study of pressure-induced polymorphic and crystal-to-amorphous transitions and in some remarks on the thermoelastic mechanism for homogeneous (mechanical) melting, a process which defines an upper limit of metastability.