PREPARATION AND CRYSTAL-STRUCTURE OF RB2N I3SE4

The compound Rb2Ni3Se4 was synthesized by heating a mixture of rubidiu m carbonate, nickel and selenium at 850 degrees C in an atmosphere of hydrogen. The compound has a golden lustre and crystallizes with the K 2Pd3S4-type structure; a = 10.555(3) Angstrom, b = 27.588(6) Angstrom, c = 6.031(6) Angstrom, Z = 8, Fddd (No. 70). The structure can be des cribed as a stacking of layers of the composition Rb2Ni3Se4 with a sta cking sequence abcd. The electrostatic part of lattice energy (MAPLE) will be discussed for compounds of the compositions A(2)M(3)X(4) (A co rresponds to K, Rb, Cs; M corresponds to Ni, Pd, Pt and X corresponds to S, Se).