Structural phase transition in Li2C2

Pure polycrystalline Li2C2 could be obtained by the reaction of lithium and graphite flakes in an are-melting furnace. X-ray powder investigations on these samples confirm the crystal structure given by Juza, Wehle, and Schus ter (Immm, No.71, Z=2) which is isotypic to Rb2O2 and Cs2O2. At about 500 d egrees C a reversible phase transition (1(st) order) to a cubic modificatio n (Fm (3) over bar m, No. 225, Z = 4) has been observed. This high temperat ure modification can be described as an antifluorite-structure with disorde red C-2(2-) dumbbells.