Under subvalent doping, the two models give even more strongly divergent predictions; the lithium-only defect model underestimates the doping threshold at which a significant increase in concentration of lithium interstitials is observed by several orders of magnitude. This effect can be understood by considering the conventional "Schottky pair" description of defect disorder in Li 3 OCl; the dominant positively charged defect species is the chlorine vacancy, V Cl , and subvalent doping therefore prin-cipally increases the concentration of this non-chargecarrying host-framework defect ahead of the minority Li i defects.