2 EXAMPLES OF PARTIAL AND TOTAL DEFECTS IN THE BA-CENTER-DOT-LN(2)MO(4)O(16)-TYPE - BACU0.41-CENTER-DOT-0.59PR2MO4O16 AND BA-CENTER-DOT-YB2MO4O16

Single crystals of (I) BaCu0,41Pr2Mo4O16 and (II) BaYb2Mo4O16 have bee n prepared by flux technique. Both compounds crystallize with monoclin ic symmetry, space group C-2h(6)-C2/c with (I): a = 5.352(11), b = 12. 888(2), c = 19.399(4) Angstrom; beta = 90.89(3)degrees; (II): a = 5.18 1(7), b = 12.467(3), c = 19.350(3) Angstrom, beta = 91.93(2)degrees, Z = 4. The crystal structure is characterized by (1)(infinity) [BaMO(12 )]-chains along [010]. In the first case the M positions are occupied by copper by about 41%, in the second case these positions remain comp letely unoccupied. With respect to the crystal chemistry of the refere nce compound Ba(Cu0.22Mg0.78)Nd2Mo4O16 all substances of the compositi on BaLn(2)Mo(4)O(16) should be written as Ba square Ln(2)Mo(4)O(16) in dicating the holes in the (1)(infinity) [BaMO(12)]-chains by square.