Abstract
The behavior of alkaline carbonates at high pressure is poorly understood. Indeed, theoretical and experimental investigations of the pressure induced structural changes have appeared in the literature only sporadically. In this article we use evolutionary crystal structure prediction algorithms based on density functional theory to determine crystal structures of high-pressure phases of Li2CO3, Na2CO3, and K2CO3. Our calculations reveal several new structures for each compound in the pressure range of 0-100 GPa. Cation arrays of all high-pressure structures are of the AlB2 topological type. The comparison of cation arrays of ambient, and high-pressure structures with that of binary A(2)B compounds indicates an analogy between high-pressure behavior of alkaline carbonates and alkaline sulfides (oxides, selenides, tellurides), which under compression go through the following series of phase transitions: anti-CaF2 -> anti-PbCl2 -> Ni2In -> AlB2. All structures presented in this trend are realized in the high-pressure trend of alkaline carbonates, although some intermediary structures are omitted for particular compounds.