Towards Li-poor conditions (point B), H Li and HO Cl quickly become the dominant species with formation energies at E F under point B of around 0.42 and 0.37eV respectively. As both defects are neutral (q=0), they aren't expected to be charge compensated by any intrinsic or otherwise H-related species. The equilibrium concentrations of [H Li ] and [HO Cl ] are fairly high ∼ 1 × 10 20 cm -3 and ∼ 2 × 10 20 cm -3 respectively. It is important to note, that whilst "equilibrium concentrations" are stated, we are constrained by the formation of Li 3 OCl and it is highly likely that in reality excess H will make its way into the structure increasing H defect concentrations, or form additional Li 3 -x OH x Cl phases or Li 2 OHCl. Upon H doping under Li-poor conditions, E F again, shifts towards the conduction band minimum (CBM) from 1.37eV to 1.7eV resulting in a lower effective formation energy of V Li from ∼ 1.18 eV to ∼ 0.84 eV. As at point A, it is expected that [V Li ] rises from ∼ 6 × 10 14 cm -3 when undoped to ∼ 1.4 × 10 17 cm -3 . Figure (a) and (b) show the relaxed defect supercells of HO Cl (at q=0), and H Li (at q=0) respectively. HO Cl , warps the structure shifting adjacent Li away from its preferred site (Wyckoff: 3c ) towards the neutral cluster. As this defect is nominally neutral, the displacement arises due to the smaller OH -radii (110pm) compared to Cl -radii (181pm) and may aid in improving Li-ion transport by increasing "accessible space" and weakening the Li-O bonds. In H Li ( 4 (b)), H shifts off its Li site (3c) towards an adjacent O forming a neutral OH. This defect can therefore be seen as a "pseudo-V Li " or as suggested by Song et al. a Frenkel-type defect as any moving Li into this space technically becomes an interstitial. Experimentally, Schwering et al. suggested H Li as the dominant defect, remarking also that H Li provides rotatable OH that facilitates Li transport. Work carried out by Eilbracht et al. using single crystal data on Li 2 OHCl also suggest Li site occupation. Similar evaluations of the role of rotatable OH groups have been suggested in the literature. Dawson et al. using molecular dynamics simulations (MD) combined with 2 H NMR spectroscopy, observe that both highly rotatable OH groups exist alongside fixed OH groups. Further investigation shows that OH rotations are more free when O is coordinated to fewer lithiums.