Premium
The Real Structure of YbSi 1.4 ‐ Commensurately and Incommensurately Modulated Silicon Substructures
Author(s) -
Kubata Christof,
Krumeich Frank,
Wörle Michael,
Nesper Reinhard
Publication year - 2005
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200400423
Subject(s) - high resolution transmission electron microscopy , crystallography , orthorhombic crystal system , superspace , group (periodic table) , crystal structure , niobium , tetrahedron , electron diffraction , materials science , transmission electron microscopy , chemistry , physics , nanotechnology , diffraction , optics , organic chemistry , supersymmetry , metallurgy , mathematical physics
A systematic thermochemical investigation of the binary system Yb/Si revealed the phase YbSi 1.4 in pure form that is accessible by reacting the elements at 890 °C in sealed niobium ampoules. According to XRD investigations, the basic structure of YbSi 1.4 is orthorhombic (space group: Cmcm ; a = 4.159(1), b = 23.510(5), c = 3.775(1) Å). The structure contains blocks with three sheets of trigonal Yb 6 prisms that are connected to each other by face‐sharing. Two of these prism sheets are fully occupied by Si whereas the middle one is occupied by ∼ 80 % only, as obtained from the electron density distribution by XRD. Transmission electron microscopy (TEM) investigations show the presence of two distinct ordering variants: YbSi 1.4 ‐I has a unit cell with doubled volume (space group of the structural model: Imm 2; a I = 4.16, b I = 7.56, c I = 23.51Å). In the structural model derived from HRTEM images, Si fills 3/4 of the partly occupied Yb 6 prisms in a regular way. YbSi 1.4 ‐II exhibits an incommensurate modulation that can be described in the 3 + 1 dimensional superspace group Cmcm (10γ) (No. 63.3). The evaluation of HRTEM images of YbSi 1.4 ‐II revealed parallel domains with the structure of YbSi 1.4 ‐I, with the modulation due to a shift of the domains with respect to each other.