J. Phys. IV France
Volume 7, Numéro C2, Avril 1997Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure
|C2-263 - C2-264
J. Phys. IV France 7 (1997) C2-263-C2-264
Combined Multiple Scattering Simulation and Hartree-Fock LCAO Studies of Atomic Displacements in LixV2O5F. Lemoigno, E. Prouzet, Z.Y. Wu, P. Gressier and G. Ouvrard
Institut des Matériaux de Nantes, UMR 110, CNRS-Université de Nantes, 2 rue de la Houssinière, 44072 Nantes cedex 03, France
Lithium intercalation into the lamellar vanadium oxide LixV2O5 is only reversible below x ≈ 0.9. Insertion of larger amounts induces an irreversible phase transition that destroys the 2D character of the host. This structural change is due to atomic displacements that lead from distorted square pyramidal V2O5clusters to V2O6 octahedra . In-situ XAS studies at the vanadium K edge of lithium intercalation into V2O5 confirmed this local increase of the symmetry and established that, not only oxygen but also vanadium, move from their initial sites, as the intercalation proceeds . Starting from this structural model, we performed multiple scattering simulation (CONTINUUM code) to understand the changes observed in the experimental XANES spectra. These calculations explain the new features appearing in the edge as the lithium rate increases. Hartree-Fock LCAO calculations (CRYSTAL 92 code) have also betn used to discuss the stability of the proposed structural models, taking into account both atomic displacements and lithium intercalation.
© EDP Sciences 1997