Crystal chemistry of lithium: oxygen coordination and bonding
Wenger, Marc; Armbruster, Thomas
European Journal of Mineralogy Volume 3 Number 2 (1991), p. 387 - 400
published: Apr 18, 1991
manuscript accepted: Sep 26, 1990
manuscript received: Mar 12, 1990
ArtNo. ESP147050302010, Price: 29.00 €
Abstract The oxygen coordination of Li is investigated on the basis of structural data retrieved from a data bank. Tetrahedral Li with = 1.96 Å is the dominant coordination. Strong oxygen-oxygen edge distortions occur when Li tetrahedra share edges with other tetrahedra or octahedra. Octahedral Li with = 2.15 Å is often strongly distorted with large variations of individual Li-O distances within the same polyhedron. Seven examples show five-fold coordinated Li. A simplified potential energy model is used to calculate energies for ideal LiOn (n = 3,4,6,8) polyhedra. Quadratic force constants are derived for Li-O stretching and Li displacement within an ideal tetrahedron and octahedron. These calculations predict that the Li vibration along the Li-O vector has a similar amplitude in Li04 tetrahedra as in LiO6 octahedra. Anisotropic displacement parameters for various LiO3, LiO4, LiO5, and LiO6 polyhedra are extracted from the recent literature. Mean difference displacement parameters calculated along the Li-O vector show no dependence with the coordination number (n = 3,4,5,6) which agrees with the estimated force constants for out-of-centre Li displacements.