Lithium uptake in strontium chlorapatite – A combined experimental and first principles study

Highlights: • Preferential occupancy of lithium in strontium chlorapaties studied. • NMR experiments coupled with DFT calculations show that lithium occupies 8- coordinated Sr site. • Both calculated and measured NMR chemical shifts indicate a distribution of local environments around lithium. Preferential site occupancy of lithium in the phosphate based mineral strontium chlorapatite has been studied using solid state NMR spectroscopy and first principles calculations. ³¹P Magic Angle Spinning (MAS) NMR shows evidence for strontium being substituted by lithium. The results are discussed on the basis of incommensurate lattice and lattice distortion caused by Li substitution. Detailed analysis of the ⁷Li MAS NMR spectra as well as ab-initio calculations show preferential occupation of lithium in eight coordinated cation site (M(II)) rather than the nine coordinated M(I) site and also distribution of the local environment around the cation ion site.