Kinetics of Growth of Columnar Triclinic Calcium Pyrophosphate Dihydrate Crystals

Abstract

Rates of growth of triclinic calcium pyrophosphate dihydrate microcrystals of columnar shape are reported for pH 4.5, 5.0, 5.5, and 6.5. These rates can be explained by the polynuclear growth mechanism in which nuclei of critical size form, grow laterally, and intergrow while spreading over the surface. The surface energy is found to be 75 ± 5 mJ/m 2 . The frequency for attachment of calcium ions to the crystal surface is found to be (2 ± 1) × 10 5 s -1, close to the theoretical value for a calcium ion to partially dehydrate and simultaneously make a diffusion jump into a kink site, 1.6 × 10 5 s -1 .