Simulation of NMR Fermi Contact Shifts for Lithium Battery Materials: The Need for an Efficient Hybrid Functional Approach

Abstract

In the context of the development of NMR Fermi contact shift calculations for assisting structural characterization of battery materials, we propose an accurate, efficient, and robust approach based on the use of an all electron method. The full-potential linearized augmented plane wave method, as implemented in the WIEN2k code, is coupled with the use of hybrid functionals for the evaluation of hyperfine field quantities. The WIEN2k code uses an autoadaptive basis set that is highly accurate for the determination of the hyperfine field. Furthermore the implementation of an onsite version for the Hartree–Fock exchange offers the possibility to use hybrid functional schemes at no additional computational cost. In this paper, NMR Fermi contact shifts for lithium are studied in different classes of paramagnetic materials that present an interest in the field of Li-ion batteries: olivine LiMPO4 (M = Mn, Fe, Co, and Ni), anti-NASICON type Li3M2(PO4)3 (M = Fe and V), and antifluorite-type Li6CoO4. Making use of the possibility to apply partial hybrid functionals either only on the magnetic atom or also on the anionic species, we evidence the role played by oxygen atoms on polarization mechanisms. Our method is quite general for an application on various types of materials. Furthermore, it is very competitive compared to the other methods recently proposed that are based either on a plane wave basis set with a PAW implementation or on an LCAO one with a full potential description.