Copper Weberites: Crystal Structure and Magnetic Investigation of Na₂CuGaF₇ and Na₂CuInF₇

Abstract

Abstract The crystal structures of two new copper weberites Na 2 CuGaF 7 and Na 2 CuInF 7 have been determined. Na 2 CuGaF 7 has the monoclinic space group C2/c: a = 1232.5(5) pm, b = 731.8(1) pm, c = 1278.0(5) pm, β = 109.29(2)° and Z = 8. Na 2 CuInF 7 crystallizes in the orthorhombic space group Pmnb: a = 731.8(1) pm, b = 1060.2(2) pm, c = 771.2(1) pm and Z = 4. The structures have been refined from 1175 reflections to R = 0.043 (wR = 0.035) for Na 2 CuGaF 7 , and from 1917 reflections to R = 0.034 (wR = 0.025) for Na 2 CuInF 7 . The structures consist of [CuF 5 ] n 3n− chains which are parallel the a‐axis in Na 2 CuInF 7 and oriented in two alternating directions in Na 2 CuGaF 7 . Sodium atoms exhibit either seven‐fold or eight‐fold coordination. Although strong antiferromagnetic interactions are observed inside the chains, there is no evidence for three‐dimensional ordering.