DFT Models to Explore Structures and Properties of Novel Carbonates
Carbonates are an important mineral group and therefore, their stabilities and properties have been extensively investigated. Specifically, due to their important role in the deep carbon cycle, numerous high pressure studies have been carried out. Until 2011, anhydrous carbonates were thought to overwhelmingly consist of nearly planar trigonal CO32--groups, in which the carbon orbitals are sp2-hybridised, stacked in a variety of arrangements with either divalent cations or monovalent/trivalent cations. The experimental discovery of sp3-carbonates [1], where the fundamental building units are four-fold coordinated carbon atoms, expanded our knowledge of the crystal chemistry of carbonates and provided a new building block for high pressure carbonates [2]. The sp3-carbonates show a rich structural diversity, as the CO44--groups may polymerize to form clusters, groups or chains (see summary in [3]). About 16 sp3-carbonates have been structurally characterized up to now, and some of them can actually exist as metastable polymorphs at ambient conditions. More recently, yet another group of carbonates, the inorganic pyrocarbonate salts SrC2O5 and PbC2O5, containing isolated C2O52--anions, have been synthesized [3,4].
In this contribution, I will discuss how DFT-models are instrumental in the discovery of novel carbonates, and how atomistic model calculations complement the experimental investigations, thus allowing a deep under- standing of the structure-property relations of carbonates and of the role these carbonates play in nature.
Acknowledgments
Bjoern Winkler is grateful for support within the BIOVIA Science Ambassador program. Funding has generously been provided by the German Science Foundation, DFG, within projects BA-4020, WI-1232, and DFG-FOR2125 “CarboPaT”. We have benefitted from beam time at DESY/PETRA III and the ESRF.
References
[1] Boulard, E., Gloter, A., Corgne, A., Antonangeli, D., Auzende, A.-L., Perrillat, J.-P., Guyot, F., Fiquet, G.: New host for carbon in the deep Earth. PNAS 108, 5184–5187 (2011). https://doi.org/10.1073/pnas.1016934108 ;
[2] König, J., Spahr, D., Bayarjargal, L., Gavryushkin, P.N., Milman, V., Liermann, H.-P., Winkler, B.: Novel cal- cium sp3-carbonate CaC2O5-I42d may be a carbon host in Earth’s lower mantle. Earth. Space. Chem. 6, 73–80 (2022). https://doi.org/10.1021/acsearthspacechem.1c00284
[3] Spahr,D., Binck, J., Bayarjargal, L., Luchitskaia, R., Morgenroth, W., Comboni, D., Milman, V., Winkler, B.: Tetrahedrally Coordinated sp3‐Hybridized Carbon in Sr2CO4 Orthocarbonate at Ambient Conditions. In- org. Chem. 60, 5419–5422 (2021). https://doi.org/10.1021/acs.inorgchem.1c00159 ;
[4] Spahr, D., König, J., Bayarjargal, L., Milman, V., Perlov, A., Liermann, H.-P., Winkler, B.: Sr[C2O5] is an In- organic Pyrocarbonate Salt with [C2O5]2− Complex Anions. J. Am. Chem. Soc. 144, 2899–2904 (2022). https://doi.org/10.1021/jacs.2c00351 ;
[5] Spahr, D., König, J., Bayarjargal, L., Luchitskaia, R., Milman, V., Perlov, A., Liermann, H.-P., Winkler, B.: Synthesis and Structure of Pb[C2O5]: An Inorganic Pyrocarbonate Salt. Inorganic Chemistry 61, 9855– 9859 (2022). https://doi.org/10.1021/acs.inorgchem.2c01507 ;
