STRUCTURAL AND ELECTRONIC-PROPERTIES OF K2NI3S4, A PSEUDO-2 DIMENSIONAL COMPOUND WITH A HONEYCOMB-LIKE ARRANGEMENT

Air sensitive single crystals of K2Ni3S4 have been synthesized by reac tion of 1Ni,2K(2)S and 4S in an evacuated silica tube at 750 degrees C for 6 days. The structure was solved in the Fddd space group with a = 5.723(2) Angstrom, b = 10.040(3) Angstrom and c = 26.059(7) Angstrom. The refinement led to R(F) = 0.038 (R(wF), = 0.045) for 23 variables and 392 reflections. The crystal structure can be described along the c-axis as the succession of [Ni,S-4(2-)] infinite layers separated by two alkali metal cation slabs. In the [Ni3S42-] layers, the nickel ato ms are in sulfur square planar coordination. The (NiS4) square planes are linked together by edge sharing in such a way as to define a honey comb network. Despite the occurrence of short S ... S contacts perpend icular to the slabs, electrical measurements and tight-binding band st ructure calculations suggest the classical overall charge balance (K2N i3S4-II)-Ni-I-S-II.