Gray Danielle L, Francisco Melanie C, Kanatzidis Mercouri G
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
Inorg Chem. 2008 Aug 18;47(16):7243-8. doi: 10.1021/ic801080f. Epub 2008 Jul 25.
YCo 0.88Ga 3Ge has an incommensurately modulated structure that was solved with (3 + 1)D superspace techniques. YCo 0.88Ga 3Ge crystallizes in the orthorhombic superspace group Immm(alpha00)00 s with unit cell constants of a = 4.1639(4), b = 4.1639(4), c = 23.541(2) A and a modulation vector of q = 0.3200(4) a* at 293 K. The incommensurate modulation, which creates a very large supercell ( approximately 25 fold), arises from a charge density wave (CDW) in the square net of Ga atoms that is coupled with a site occupancy wave (SOW) of Co atoms. The distorted Ga net features polygallide ribbons, chains, as well as single atoms. Temperature dependent crystallographic studies of the structure from 100-500 K indicate that the CDW is "locked in". Electrical conductivity and thermopower measurements in the temperature range of 300-500 K show that YCo 0.88Ga 3Ge is a poor metal.
