Crystallographic and magnetic structure of Li2MnO3

The structure of Li2MnO3 was refined on a single crystal: space group C2m, a = 493.7(1), b = 853.2(1), c = 503.0(2) pm, β = 109.46(3)°, Z =4, R = 0.020, Rw = 0.027 for 619 independent reflections with I > 5σ. Distortions in the ordered rocksalt superstructure are induced by the cis positions of Mn4− in the O2 coordination octahedra. Powders of Li2MnO3 are slightly disordered with 12 ± 3% Mn on the Li sites. They are antiferromagnetic with TN = 36.5 K; the cell is doubled along c, corresponding to opposite moments on alternating Mn-containing layers along c. A comparison of structural data of rocksalt-related A2BO3 compounds (A = Li, Na; B = tetravalent metal) shows that many previously reported cells could be indexed in smaller monoclinic or hexagonal cells.