Crystal Structure of Li₂MgSiO₄

L. D. Iskhakova* and V. B. Rybakov**

* Fiber Optics Research Center, Institute of General Physics,
Vavilova ul. 38, Moscow, 119992 Russia

e-mail: ldisk@fo.gpi.ru

** Department of Chemistry, Moscow State University,
Vorob’evy gory, Moscow, 119992 Russia

Received March 21, 2002

Abstract—The crystal structure of Li₂MgSiO₄ was established by single-crystal X-ray diffraction analysis.
The crystals are monoclinic, a = 4.9924(7) Å, b = 10.681(2) Å, c = 6.2889(5) Å, = 90.46(1)°, Z = 4,
sp.gr.2₁/n, V = 335.54 Å , R = 0.062. In a Li₂MgSiO₄ crystal, four types of independent T(1–4) tetrahedra
share vertices to form a three-dimensional framework. Three of these tetrahedra are occupied simultaneously
by Li and Mg cations, which corresponds to the crystallochemical formula (Li_0.98Mg_0.02)(Li_0.80Mg_0.20)
(Li_0.22Mg_0.78)SiO₄ . In slightly distorted SiO₄ tetrahedra denoted as T(1), the average Si–O distance is 1.635(2) Å.
The distortions of other tetrahedra and the average (Li_xMg_1x)O distances increase with an increase in lithium
content. These distances in the T(2), T(3), and T(4) tetrahedra are 1.955(2), 1.971(4), and 2.019(6) Å, respec-
tively. The structure of the new compound is compared with the crystal structures of other Li₂M²⁺SiO₄ com-
pounds and the luminescence spectra of Cr⁴⁺ : Li₂MgSiO₄ . © 2003 MAIK “Nauka/Interperiodica”.

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