Potassium carbonate under pressure: common structural trend for alkaline carbonates and binary compounds

TL;DR

This study combines theoretical and experimental methods to reveal a common structural trend in high-pressure phases of alkaline carbonates, showing they mirror the ambient structures of heavier group elements.

Contribution

It introduces a unified structural trend for high-pressure phases of alkaline carbonates based on combined ab-initio calculations and experimental data.

Findings

High-pressure phases of K2CO3 follow a structural trend similar to heavier group element compounds.

The trend is confirmed by consistent pressure-induced transformations in various binary A2B compounds.

The approach unifies understanding of structural changes in alkaline carbonates under pressure.

Abstract

The behaviour of alkaline carbonates at high pressure is poorly understood. Indeed, theoretical and experimental investigations of general trends of pressure induced structural changes appear in the literature only sporadically. In this article we use a combination of ab-initio calculations and high-pressure experiments in diamond anvil cell to determine crystal structures of high-pressure phases of K2CO3. The comparison with experimental data on Li2CO3 allows to reconstruct the common structural trend, which is consistent with the simple rule that the structure of high-pressure polymorph is the same as the ambient structure of a heavier element compound from the same group of the periodic table. The correctness of the constructed trend is confirmed by the perfect consistency with pressure-induced structural transformations in a wide range of binary A2B compounds.