In-Situ NMR Investigation of Dynamical Behavior of Point and Line Defects During Deformation of NaCl

Abstract

ABSTRACTSpin lattice relaxation time in the rotating frame [T1ρ] is investigated in pure NaCl single crystals as a function of temperature in-situ during deformation. Transition from 2- phonon Raman process to atomic diffusion was noted at around 500K in the undeformed material and the activation energy was determined to be that for the diffusion of extrinsic vacancies. Enhanced spin relaxation rates were noted during constant strain-rate deformation at temperatures from ambient to about 750K. These enhancements were identified to arise from dislocation motion at lower temperatures while enhanced diffusion due to excess vacancies at higher temperatures. This excess concentration increased with increased strain-rate and in-situ annealing of deforma-tion induced excess vacancies is noted at high temperatures.