It was recalled that experiments had indicated that atomic tunnelling defects existed in plastically deformed metals, but it was not clear how this was possible; given the large mass of metal atoms. By using classical molecular dynamics calculations, structures, energy barriers, effective masses and quantum tunnelling rates were determined for dislocation kinks and jogs in screw dislocations. It was found that jogs were unlikely to tunnel, but that kinks could exhibit large quantum fluctuations. The kink motion involved hundreds of atoms; each of which shifted by a tiny amount, and led to a small effective mass and tunnelling barrier.

Calculation of Quantum Tunnelling for a Spatially Extended Defect - the Dislocation Kink in Copper Has a Low Effective Mass. T.Vegge, J.P.Sethna, S.A.Cheong, K.W.Jacobsen, C.R.Myers, D.C.Ralph: Physical Review Letters, 2001, 86[8], 1546-9