Radiation growth of hcp crystals driven by discrete breathers

Abstract

A new mechanism of radiation growth (RG) of hexag-onal close pack (hcp) crystals is proposed, which is based on the radiation-induced creation of moving ‘discrete breathers’ (DBs), i.e. large amplitude anharmonic lattice vibrations, which can propagate and transfer energy along close-packed crystallographic directions within the basal planes of and excite atoms at prismatic faces/edges. Ac-cordingly, the DB-induced vacancy emission from pris-matic faces is enhanced as compared to that from the basal faces, at which only thermally activated vacancy emission takes place. This should result in the vacancy diffusional flow from prismatic to basal faces leading to expansion along the a-directions and to contraction along the c-axis, i.e. to the radiation-induced growth. The RG rate driven by this mechanism is evaluated in the framework of a rate theory modified with account of the DB-induced vacancy emission.