TANTALUM AND NIOBIUM DISULFIDES INTERCALATED WITH CHROMIUM AND NICKEL

X-ray diffraction analysis of Cr1/3-xNixTaS2 (0 less than or equal to x less than or equal to 1/3) intercalation compounds shows that the ch romium and nickel atoms randomly occupy octahedral sites 2a (0, 0, 0) of the 2H-TaS2 structure (sp. gr. P6(3)/mmc). Neutron diffraction stud ies in the temperature range 1.5-293 K show that, on cooling, Ni1/3TaS 2 undergoes a structural transformation. In the resulting superstructu re (sp, gr. P6(3)(2)2, a = root 3 a(0)), the nickel atoms are distribu ted nonuniformly over crystallographic positions 2b (0, 0, 1/4), 2c (1 /3, 2/3, 1/4), and 2d (2/3, 1/3, 1/4). Under similar conditions, the C r0.03Ni0.30TaS2 intercalation compound undergoes no structural transfo rmations. Neither Ni1/3TaS2 nor Cr0.03Ni0.30TaS2 show antiferromagneti c ordering. According to x-ray diffraction data for Cr1/3NbS2, the int ercalated chromium atoms randomly occupy octahedral sites 2a (0, 0, 0) of the 2H-TaS2 structure (sp. gr. P6(3)/mmc). In the P6(3)22 superstr ucture of the Cr1/3-xNixNbS2 (0.1 less than or equal to x less than or equal to 0.33) intercalation compounds, the intercalated atoms are di stributed nonuniformly over crystallographic sites, with the relative site occupancy decreasing in order (1/3, 2/3, 1/4), (0, 0, 1/4), and ( 2/3, 1/3, 1/4).