title: In1.06Ho0.94Ge2O7: a thortveitite-type compound.
abstract: A new indium holmium digermanate, In(1.06)Ho(0.94)Ge(2)O(7), with a thortveitite-type structure, has been prepared as a polycrystalline powder material by high-temperature solid-state reaction. This new compound crystallizes in the monoclinic system (space group C2/c, No. 15). The structure was characterized by Rietveld refinement of powder laboratory X-ray diffraction data. The In(3+) and Ho(3+) cations occupy the same octahedral site, forming a hexagonal arrangement on the ab plane. In their turn, the hexagonal arrangements of (In/Ho)O(6) octahedral layers are held together by sheets of isolated diortho groups comprised of double tetrahedra sharing a common vertex. In this compound, the Ge(2)O(7) diortho groups lose the ideal D(3d) point symmetry and also the C(2h) point symmetry present in the thortveitite diortho groups. The Ge-O-Ge angle bridging the diortho groups is 160.2 (3) degrees, compared with 180.0 degrees for Si-O-Si in thortveitite (Sc(2)Si(2)O(7)). The characteristic mirror plane in the thortveitite space group (C2/m, No. 12) is not present in this new thortveitite-type compound and the diortho groups lose the C(2h) point symmetry, reducing to C(2).
authors.affiliation: Instituto de Física, Universidad Nacional Autónoma de México, AP 20-364, 01000 México DF, Mexico. erickj@fisica.unam.mx
authors.forename: Erick A
authors.initials: EA
authors.lastname: Juarez-Arellano
authors.forename: Ivonne
authors.initials: I
authors.lastname: Rosales
authors.forename: Alicia
authors.initials: A
authors.lastname: Oliver
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Ruvalcaba
authors.forename: Raul E
authors.initials: RE
authors.lastname: Carbonio
authors.forename: Lauro
authors.initials: L
authors.lastname: Bucio
authors.forename: Eligio
authors.initials: E
authors.lastname: Orozco