INTERNAL FRICTION IN THE ALKALI METALS

Internal friction measurements in the alkali metals show that in Potassium there exists a γ-peak around 50K at about 10 kHz. It is due to the double kink formation in screw dislocation and has an activation enthalpy of ƉH=0.046 ± 0.003 eV. In Sodium and Lithium which undergo low temperature phase transformations there is no evidence of a similar peak above their resp. transformation temperature. This suggests in Sodium and Lithium a different structure of screw dislocations