On the crystal structure of lithium peroxide, Li2O2
  The two published lithium peroxide structures, both ascribed to the hexagonal P -6 space group, were subjected to reinterpretation and another more symmetric structure, now belonging to the P 63/m m c space group, was found. Detailed density-functional quantum mechanical calculations and crystal structure optimisations were carried out on both structures and the energetic arguments obtained therewith helped to rule out one of them. 
Luis Guillermo Cota and Pablo de la Mora