Atomic force microscopic observation of facet formation on various faces of aragonite in aqueous acetic acid

Stabilities of crystal faces of aragonite-type strontianite (SrCO3) and cerussite (PbCO3) compared by AFM observation of facet formation in acid

“…3(a), however, the positive charges at the top layer are partly canceled by the negative charges of the O atoms pointing up from the second layer. The diminished polarity and the small numbers of bond breaking make these faces fairly stable [6]. It is, thus, reasonable that these faces are commonly observed in natural crystal forms shown in Fig.…”

“…The resulting surfaces are classified as electrically neutral faces, because the center of mass of both cations and anions sit on the same plane. Since the negative charge of one O atom per each carbonate ion pops out of the plane, however, the surfaces have electric dipoles with perpendicular component [6]. The polarity and the higher number of bond-breaking make the neutral faces rather unstable in aqueous solutions.…”

Stabilities of crystal faces of anhydrite (CaSO4) compared by AFM observation of facet formation processes in aqueous solutions

“…We have compared relative stabilities of aragonite (CaCO 3 ) faces in dilute aqueous acetic acid and have found that the equilibrium form of the crystal in the acidic condition should be totally different from natural forms, probably obtained in alkaline environments [1,2]. Protonation of carbonate ions changes charge distributions at the surfaces.…”

“…Apparently polar crystal faces of aragonite are stabilized by neutralization of positive charges of Ca 2 + on the top layer, by the negative charges of O atoms pointing out of the carbonate layer at lower levels [1,2].…”

Atomic force microscopic studies of stabilization of NaCl(1 1 3), (1 1 2) and (1 1 0) surfaces in ethanol, CdCl2/ethanol and HgCl2/ethanol

“…Previously, one of the authors compared stabilities of crystal faces of the aragonite (CaCO 3 ) by observing the facet formation in etch pits during the dissolution of the crystal faces with AFM [7,8]. In an acidic solution, the (1 0 0) face which does not appear in natural crystal forms was stabilized and became atom-flat.…”