NMC 111 space group does not match with literature?!

Materials Project
1

Hello,

I am trying to perform some DFT calculations for NMC 111 (a battery cathode material: Li3NiMnCiO6). The structure available in materialsprojects has the C2 space group symmetry, while, it is widely accepted that this material has the R-3m symmetry. Can anyone tell me why we have this discrepancy? Or how can I convert the C2 structure into the R-3m structure?

Thanks

2

See the publication Crystal structure and cathode properties of delithiated Li1-xMn1/3Ni1/3Co1/3O2 for Mg rechargeable batteries, Crystal structure and cathode properties of delithiated Li1-xMn1/3Ni1/3Co1/3O2 for Mg rechargeable batteries - ScienceDirect. For the R-3m structure, the three metals {Mn,Ni,Co} have equal probability of occupying the same site. Typical DFT calculations don’t handle this sort of disorder, so it is likely that the structure on the Materials Project site is an ordered model of the R-3m structure with lower symmetry. If you need a model with R-3m structure, perhaps consider taking the delafossite structure (NaFeO2) and replace sodium with lithium.