CRYSTAL-STRUCTURE DETERMINATION OF LI2CA4SI4O13

We synthesized the compound Li2Ca4Si4O13, M(r) = 494.5, triclinic, spa ce group P1BAR, a = 10.450(3), b = 8.231(3), c = 7.170(2) angstrom, al pha = 77.71(2)-degrees, beta = 90.06(2)-degrees, gamma = 109.25(2)-deg rees, V = 567.3(5) angstrom3, Z = 2. The structure is composed of two types of silicate anions: isolated (SiO4)-4 tetrahedra and infinite ch ains (Si3O9)-6 along the [001] axis with three tetrahedra in the repea t unit. Calcium-distorted octahedra form infinite ribbons along the 10 01] axis. These ribbons are joined in the plane (010) by silicate chai ns (Si3O9)-6 to form a layer of Ca octahedra and silicate anions. The isolated tetrahedra (SiO4)-4 join two different ribbons related by a c enter of symmetry. The structure is completed by Li+ ions in distorted tetrahedral sites. (C) 1994 Academic Press, Inc.