Fast screening of solid-state lithium-ion conductors*

We present an efficient approximation to the potential energy surface of density functional theory to model the diffusion of Li ions in solid-state structures. Firstly, we assume no dependence of the electronic charge density on the position of the Li ions. Secondly, we constrain the positions of the host-lattice atoms to equilibrium and construct a Hamiltonian framework with this constant charge density. Contributions to the forces on the Li ions in a pseudopotential framework stem from the ion-ion Coulomb repulsion, the electrostatic interaction with the charge density and from the non-local projectors on the wavefunctions. The validity of the model is established by comparison with first-principles molecular dynamics simulations at frozen host-lattice for several ionic conductors at different temperatures.
We show excellent agreement for forces, power spectra and diffusion coefficients. Such development allows to screen large databases for candidate solid-state electrolytes, and we present a working high-throughput screening implementation based on the AiiDA materials' informatics platform.