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Modeling Short-Range Order in Disordered Rocksalt Cathodes by Pair Distribution Function Analysis
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DOI：10.1021/acs.chemmater.2c03827.png)
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Abstract
En 中文
Pair distribution function (PDF) analysis is a powerfultechniquefor the characterization of short-range order (SRO) in disorderedmaterials. Accurate interpretation of experimental PDF data is criticallyreliant on the development of structural models that can account forlocal variations in site occupancies and bond lengths. To this end,we outline an approach to model SRO using first-principles calculationsbased on the cluster-expansion formalism. These methods are validatedon neutron scattering data from two disordered rocksalt oxyfluorides,Li1.3Mn0.4Ti0.3O1.7F0.3 and Li1.3Mn0.4Nb0.2Ti0.1O1.7F0.3. For each composition, wedemonstrate that an average structure without any SRO fails to reproduceseveral key features in the experimental PDF. To pinpoint the originof the suspected SRO in these materials, configurational and displaciveeffects were separately investigated using two disparate models. Specialquasi-random structures were relaxed using density functional theoryto account for local changes in bond lengths while maintaining a near-randomionic configuration. This leads to slightly improved accuracy butstill misrepresents asymmetry in the first few peaks of the PDF. MonteCarlo simulations were performed to model configurational SRO on afixed lattice, which by itself is shown to have a minimal influenceon the PDF. Instead, we find that it is the bond length relaxationswithin environments created by SRO which controls the details of thePDF, thereby highlighting the subtle but important coupling betweenconfigurational and displacive SRO in disordered materials.
Keywords:
REVERSE MONTE-CARLO
INITIO MOLECULAR-DYNAMICS
TOTAL-ENERGY CALCULATIONS
TRANSITION-METAL OXIDES
X-RAY-MEASUREMENT
DIFFRACTION
REFINEMENT
CAPACITY
Journal
IF:
7
Papers:
2.8W
Citations:
11.4W
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