On the incommensurately modulated structure of ε′-Li x V2O5 at room temperature

Abstract
Electron diffraction was used to study the lithium-intercalated V2O5 bronzes Li x V2O5. In the course of these investigations a new incommensurately modulated structure was detected at room temperature. The space group of the basic structure is Pmmn; the superspace group characterizing the one-dimensionally modulated structure is found to be Pmmn (0 γ ½). The incommensurate component γ of the modulation vector q is a function of the lithium stoichiometry and varies between γ = 0.531(4) and γ = 0.550(4) for ε′-Li x V2O5 with 0.605(3) ≤ x ≤ 0.620(3). In the present paper we propose that an important contribution to the modulation results from repulsive Li+-Li+ forces, which impose an incommensurate ordering of the Li+ ions along b* in strings of cuboctahedral cavities between adjacent V2O5 layers.

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