title: Synthesis and characterization of [PtIn6](GeO4)2O and its solid solution [PtIn6](GaO4)(2-x)(GeO4)xOx/2 (0 < or = x < or = 2): gradual color change of the solid solution from black (x = 0) to yellow (x = 2) as a consequence of quantum dot effect.
abstract: A new phase [PtIn6](GeO4)2O, a filled variant of [PtIn6](GaO4)2, and the solid solution [PtIn6](GaO4)(2-x)(GeO4)xOx/2 (0 < or = x < or = 2) were prepared and characterized. Single-crystal structure refinements show that [PtIn6](GeO4)2O is isotypic with the mineral, sulfohalite Na6FCl(SO4)2, and crystallizes in the space group Fmm (Z = 4) with a = 1006.0(1) pm. The building units of [PtIn6](GeO4)2O are isolated [PtIn6]10+ octahedra and (GeO4)4- tetrahedra, and the isolated O2- ions occupy the centers of the In6 octahedra made up of six adjacent PtIn6 octahedra. The lattice parameter of the solid solution [PtIn6](GaO4)(2-x)(GeO4)xOx/2 (0 < or = x < or = 2) varies gradually from a = 1001.3(1) pm at x = 0 to a = 1006.0(1) pm at x = 2, and the color of the solid solution changes gradually from black (x = 0) to red (x = 1) to yellow (x = 2). The cause for the gradual color change was examined by performing density functional theory electronic structure calculations for the end members [PtIn6](GaO4)2 and [PtIn6](GeO4)2O. Our analysis indicates that an oxygen atom at the center of a In6 octahedron cuts the In 5p/In 5p bonding interactions between adjacent [PtIn6]10+ octahedra thereby raising the bottom of the conduction bands, and the resulting quantum dot effect is responsible for the color change.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany. j.koehler@k.f.mpg.de
authors.forename: Jürgen
authors.initials: J
authors.lastname: Köhler
authors.forename: Holger
authors.initials: H
authors.lastname: Friedrich
authors.forename: Myung-Hwan
authors.initials: MH
authors.lastname: Whangbo
authors.forename: Antoine
authors.initials: A
authors.lastname: Villesuzanne
mesh_terms: D003116:Color; D018360:Crystallography, X-Ray; D005857:Germanium / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D008280:Magnetics; D008958:Models, Molecular; D010984:Platinum / Q000737:chemistry*; D045663:Quantum Dots
chemical_list: D005857:Germanium; D007204:Indium; D010984:Platinum