Synthesis and crystal structure of LiCuFe2(VO4)3 by Rietveld method

A new triple vanadate LiCuFe2(VO4)(3) was synthesized by a solid-state method. The compound is isotypic with mineral howardevansite, NaCuFe2(VO4)(3), and crystallizes in a triclinic system (space group <P(1)over bar> (No. 2); a = 8.1484(5), b = 9.8024(7), c = 6.6355(4) Angstrom, alpha = 103.832(3), beta = 102.353(3), gamma = 106.975(3), V = 468.68 Angstrom(3), Z = 2). Crystal structure of LiCuFe2(VO4)(3) was refined by Rietveld method with R-WP = 2.32%, R-P = 1.76%, R-I = 2.82%, S = 1.55, using X-ray diffraction. The crystal structure has five independent cation sites. Lithium cations are located in the cavities M(1)O-6 and M(5)O-10, which form infinite chains in the [001] direction and are linked through a common face. The lithium cation in the M(1)O-6 cavity has a square planar coordination. The lithium cation in the M(5)O-10 cavity is strongly displaced up to 1.2 Angstrom from the special position (0, 0, 0.5) to a half-occupied general position (0.037, 0.087, 0.40). (C) 2000 Elsevier Science Ltd.