Equilibrium Shape of 2D Nuclei Obtained from Spiral Hillocks on {010} Form of Gypsum

Growth patterns on the {010} form of gypsum crystals were investigated, under controlled temperature and supersaturation, by atomic force microscope. With the morphology of hillocks formed by growth spirals generated by screw dislocations, the two-dimensional (2D) equilibrium morphology on the {010} form of gypsum was calculated. Edge energies of the [001], [102], [101], [201], and [100] steps were obtained by measuring the spacing between hillocks steps running in the same direction. Their values range between 8 × 10−7 and 2.3 × 10−6 erg/cm. The calculated critical size of 2D nucleus on {010} form is quite large (∼3400 nm2) and witnesses the low supersaturation value at which experiments were done.