Premelting generation of interstitial defects in polycrystalline indium

High-precision measurements of the shear modulus of polycrystalline indium from room temperature to the melting temperature $T_{\mathrm{m}}$ and molecular statics computer simulation have been performed. It has been found that interstitial defects are intensely generated near $T_{\mathrm{m}}$ in a dumbbell (split) configuration and their concentration can exceed the concentration of vacancies.