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Abstract:
A new layered metal-rich telluride halide, La(2)Tel(2), has been
synthesized by heating stoichiometric mixtures of Lal(3), La, and Te
under argon at 900 degrees C, and its structure has been refined from
X- ray powder diffraction data. The compound crystallizes in the
3R-Lu2CCl2 structure type (rhombohedral space group R (3) over barm
with a = 4.5074(4) angstrom, c = 32.528(2) angstrom, and Z = 3). The
crystal structure is composed of infinite layers of edge-sharing,
Te-centered metal atom octahedra and iodine atoms separating these
layers to form three close-packed I-Ln-Te-Ln-I slabs within the unit
cell. The title compound is metallic at room temperature and exhibits
an anomaly in the resistivity around 140 K which is closely related to
changes in the a lattice parameter with temperature. The chemical
bonding and metallic properties of La(2)Tel(2) can be plausibly
understood in terms of an ionic description
(Ln(3+))(2)Te2-(I-)(2)(e)(2) where two electrons are delocalized in the
La 5d conduction band.
