Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 74: Focussed session: Theory and computation of electronic structure: new frontiers VI (jointly with HL, DS)
O 74.4: Vortrag
Donnerstag, 17. März 2011, 15:45–16:00, TRE Phy
First principle calculation on the Fermi contact shift of lithium ion in paramagnetic battery materials — •Yuesheng Zhang1, Florent Boucher1, Aurore Castets2, Dany Carlier2, and Michel Ménétrier2 — 1IMN, Nantes, France — 2ICMCB, Pessac, France
Solid state NMR in materials for lithium-ion batteries is considerably developing. In paramagnetic materials, the NMR shift of lithium is mainly contributed by the Fermi contact that can be qualitatively interpreted using chemical intuition and the concept of delocalization or polarization mechanisms. In this paper, with accurate first principle methods implemented into WIEN2k, we have obtained the spin density at the nucleus of lithium ions, and then calculated the contact shifts of lithium in several selected transition metal oxides or phosphates. The results show that the calculated values are sensitive to the exchange/correlation potential used in calculation. GGA or LDA generally overestimate the shifts, the calculated values being always shifted along positive direction comparing to the experimental ones. Adding orbital potential "U" or exact exchange on transitional metal ions can improve the results, but still some differences are found with experiments for some cases. The best agreement can be obtained when partial exact exchange potential is applied to both transitional metal and oxygen ions. This means that appropriate exchange correlation potential for transitional metals and oxygen ions is really crucial to calculate the contact shift of lithium ions. This work is funded by Agence Nationale de la Recherche (ANR-09-BLAN-0186-01)