Hydroflux synthesis and crystal structure of Tl3IO

Single-crystals of thallium(I) iodide oxide Tl3IO were obtained as by-product in a hydroflux synthesis at 473 K for 10 h. A potassium hydroxide hydroflux with a water-base molar ratio of 1.6 and the starting materials TlNO3, RhI3 and Ba(NO3)2 was used, resulting in a few black needle-shaped crystals. X-ray diffraction on a single-crystal revealed the hexagonal space group P63/mmc (No. 194) with lattice parameters a = 7.1512 (3) Å and c = 6.3639 (3) Å. Tl3IO crystallizes as hexagonal anti-perovskite (anti-BaNiO3 type) and is thus structurally related to the alkali-metal halide/auride oxides M 3 XO (M = K, Rb, Cs; X = Cl, Br, I, Au). The oxygen atoms center thallium octahedra. The [OTl6] octahedra share trans faces, forming a linear chain along [001]. Twelve thallium atoms surround each iodine atom in an [ITl12] anti-cuboctahedron. Thallium and iodine atoms together form a hexagonal close-sphere packing, in which every fourth octahedral void is occupied by oxygen.

LOW-ENERGY 4He+ SCATTERING FROM DEUTERIUM ADSORBED ON STEPPED Pd(331)

We have taken angle-resolved data for the scattering of low-energy (<1 keV) 4 He + from deuterium adsorbed on a stepped Pd (331) surface. The impact geometry was "up the staircase," i.e. the 4 He + beam was perpendicular to and directly incident onto the unshadowed <011> Pd ledge atoms. A strong quasielastic scattering signal of 4 He + from D (4 He +/D) was observed at a forward-scattering angle of θ= 25° and an incidence angle of α= 76° from the (331) normal. The results agree with shadow-cone calculations of scattering first from Pd ledge atoms followed by a second event, 4 He +/D. The resultant adsorption geometry shows D to reside in the quasi-threefold ledge site on the surface directly above the bulk fcc octahedral void. These results are consistent with the previous 4 He + scattering study of the geometrically related Pd(110)-D(ads) system.