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I15-1-X-ray Pair Distribution Function (XPDF)	Anion-polarisation–directed short-range-order in antiperovskite Li2FeSO Samuel W. Coles , Viktoria Falkowski , Harry S. Geddes , Gabriel E. Pérez , Samuel G. Booth , Alexander G. Squires , Conn O'Rourke , Kit Mccoll , Andrew L. Goodwin , Serena A. Cussen , Simon J. Clarke , Saiful Islam , Benjamin J. Morgan Journal Of Materials Chemistry A DOI: 10.1039/D2TA10037A Diamond Proposal Number(s): [27702] Open Access Show Abstract ▼ Abstract: Short-range ordering in cation-disordered cathodes can have a significant effect on their electrochemical properties. Here, we characterise the cation short-range order in the antiperovskite cathode material Li2FeSO, using density functional theory, Monte Carlo simulations, and synchrotron X-ray pair-distribution-function data. We predict partial short-range cation-ordering, characterised by favourable OLi4Fe2 oxygen coordination with a preference for polar cis-OLi4Fe2 over non-polar trans-OLi4Fe2 configurations. This preference for polar cation configurations produces long-range disorder, in agreement with experimental data. The predicted short-range-order preference contrasts with that for a simple point-charge model, which instead predicts preferential trans-OLi4Fe2 oxygen coordination and corresponding long-range crystallographic order. The absence of long-range order in Li2FeSO can therefore be attributed to the relative stability of cis-OLi4Fe2 and other non-OLi4Fe2 oxygen-coordination motifs. We show that this effect is associated with the polarisation of oxide and sulfide anions in polar coordination environments, which stabilises these polar short-range cation orderings. We propose similar anion-polarisation–directed short-range-ordering may be present in other heterocationic materials that contain cations with different formal charges. Our analysis also illustrates the limitations of using simple point-charge models to predict the structure of cation-disordered materials, where other factors, such as anion polarisation, may play a critical role in directing both short- and long-range structural correlations.	Apr 2023

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I15-1-X-ray Pair Distribution Function (XPDF)

Anion-polarisation–directed short-range-order in antiperovskite Li2FeSO