Hydrothermal synthesis, characterization and magnetic properties of NaVGe2O6 and LiVGe2O6

Supercritical fluids are shown to be an excellent reaction media for the synthesis of novel solid state phases at intermediate temperatures. LiVGe2O6 and NaVGe2O6 have the common pyroxene structure composed of VO6 linear chains. NaVGe2O6 crystallizes in the monoclinic space group C2/c with four formula units having cell dimensions a = 9.960(4) Å, b = 8.853(10) Å, c = 5.4861(10) Å, β = 106.403(3)°. The structure was refined until R = 0.0290 and Rw = 0.0370. For LiVGe2O6 in space group P21/c: a = 9.8508(7) Å, b = 8.754(3) Å, c = 5.3948(13) Å, β = 108(3)°, R = 0.0240 and Rw = 0.0250. The compounds contain edge-shared VO6 octahedral chains and corner-shared GeO4 tetrahedral chains. The presence of these VO6 chains results in spin-Peierls distortion. Structural and physical characterization of the compounds are reported.