Structures and stability of calcium and magnesium carbonates at mantle pressures

C. Pickard, R. Needs

Physical Review B 91, 104101 (2015)

#highpressure#condensedmatter#molecularstructure

Download the PDF

LQ placeholderPredicting stable structures of calcium and magnesium carbonate is crucial for understanding the Earth's deep carbon cycle.

Predicting stable structures of calcium and magnesium carbonate is crucial for understanding the Earth's deep carbon cycle.

Ab initio random structure searching (AIRSS) and density functional theory methods are used to predict structures of calcium and magnesium carbonate (CaCO3 and MgCO3) at high pressures. We find a previously unknown CaCO3 structure which is more stable than the aragonite and "post aragonite" phases in the range 32--48 GPa. At pressures from 67 GPa to well over 100 GPa the most stable phase is a previously unknown CaCO3 structure of the pyroxene type with fourfold coordinated carbon atoms. We also predict a stable structure of MgCO3 in the range 85--101 GPa. Our results lead to a revision of the phase diagram of CaCO3 over more than half the pressure range encountered within the Earth's mantle, and smaller changes to the phase diagram of MgCO3. We predict CaCO3 to be more stable than MgCO3 in the Earth's mantle above 100 GPa, and that CO2 is not a thermodynamically stable compound under deep mantle conditions. Our results have significant implications for understanding the Earth's deep carbon cycle.

LQ placeholder

Scale of non-locality for a system of n particles

S. Talaganis, I. Teimouri

Sub. to Physical Review D

LQ placeholder

How much can we influence the rate of innovation?

T. Fink, M. Reeves

Science Advances

LQ placeholder

The statistical physics of real-world networks

G. Cimini, T. Squartini, F. Saracco, D. Garlaschelli, A. Gabrielli, G. Caldarelli

Nature Reviews Physics

LQ placeholder

On defining the Hamiltonian beyond quantum theory

D. Branford, O. Dahlsten, A. Garner

Foundations of Physics

LQ placeholder

Reconstructing grain-shape statistics from electron back-scatter diffraction microscopy

R. Farr, Z. Vukmanovic, M. Holness, E. Griffiths

Physical Review Materials

LQ placeholder

Tackling information asymmetry in networks: a new entropy-based ranking index

P. Barucca, G. Caldarelli, T. Squartini

Journal of Statistical Physics

LQ placeholder

Eigenvalues of subgraphs of the cube

B. Bollobás, J. Lee, S. Letzter

European Journal of Combinatorics

LQ placeholder

Maximum one-shot dissipated work from Rényi divergences

N. Halpern, A. Garner, O. Dahlsten, V. Vedral

Physical Review E

123 / 123 papers