Size effect on the lattice parameter of KCl during mechanical milling

The size effect on the lattice parameter of ionic KCl nanocrystals was studied systematically during mechanical milling of pure KCl powder under vacuum. The results suggest anomalous lattice expansion, with the lattice parameter increasing from 6.278 Å at d = 6 μm to 6.30307 Å at d = 85 nm. The defects generated during ball milling of KCl and surface stress are deemed to be responsible for this lattice parameter expansion.