Epitaxy and Topotaxy in the Aragonite-Calcite Polymorphism

Abstract

The transformation between aragonite and calcite, the two most common CaCO₃ polymorphs, is encountered both in geological and biological (nacre-like) minerals. Recently, the origin of the new polymorph hexaragonite at room temperature and pressure and analysed in detail the homoepitaxy as a new physical phenomenon for both structures is discussed. Here, at first distinguishing epitaxy from topotaxy, which rules the main mechanisms of calcite-aragonite transitions. Then, attempt to move from qualitative to quantitative descriptions of these transitions. Hence, it will deal with 2D (epitaxy) and 3D (topotaxy) conversions in the polymorphic system, in order to gain insight into their differences, resulting from literature experiments and calculation constraints.