The crystal structures of Mn3As2(II) and Mn5As4 determined from intergrown crystals

The title compounds have closely related structures and intergrown crystals are very common. Both compounds have the same orthorhombic space group Cmc2 1 and both have - within the error limits - two translation periods in common: a = a' = 376.1(1) pm, b = b' = 1376.0(2) pm, c = 1319.0(1) pm, c' = 1212.3(2) pm, Z = 8, Z' = 4 for Mn 3 As 2 (II) and Mn 5 As 4 , respectively. Both structures were determined from one intergrown «single-crystal». The conventional residuals are R = 0.044(669 structure factors, 61 variable parameters) and R' = 0.048 (553 F's, 55 variables). The difference between the two compounds arises through the absence of one Mn position in Mn 5 As 4 . The structures are intermediate between those of NiAs and Ni 2 In