Metal Nitrides Grown from Ca/Li Flux: Ca_6Te_3N_2 and New Nitridoferrate(Ⅰ) Ca_6(Li_xFe_(1-x))Te_2N_3

摘要

Two new tellurium-containing nitrides were grown from reactions in molten calcium and lithium. The compound Ca_6Te_3N_2 crystallizes in space group R3c (a = 12.000(3)A, c = 13.147(4)A; Z = 6); its structure is an anti-type of rinneite (K_3NaFeCl_6) and 2H perovskite related oxides such as Sr_3Co_2O_6. The compound Ca_6(Li_xFe_(1-_))Te_2N_3 where x ≈ 0.48 forms in space group P4_2/m (a = 8.718(3)A, c = 6.719(2)A; Z = 2) with a new stuffed anti-type variant of the Tl_3BiCl_6 structure. Band structure calculations and easily observable red/green dichroic behavior indicate that Ca_6Te_3N_2 is a highly anisotropic direct band gap semiconductor (E_g = 2.5 eV). Ca_6(Li_xFe_(1-x)Te_2N_3 features isolated linear N-Fe-N units with iron in the rare Fe~(1+) state. The magnetic behavior of the iron site was characterized by magnetic susceptibility measurements, which indicate a very high magnetic moment (5.16μ_B) likely due to a high degree of spin-orbit coupling. Inherent disorder at the Fe/Li mixed site frustrates long-range communication between magnetic centers.