Small Polarons in Transition Metal Oxides

The formation of polarons is a pervasive phenomenon in transition metal oxide compounds, with a strong impact on the physical properties and functionalities of the hosting materials. In its original formulation the polaron problem considers a single charge carrier in a polar crystal interacting with its surrounding lattice. Depending on the spatial extension of the polaron quasiparticle, originating from the coupling between the excess charge and the phonon field, one speaks of small or large polarons. This chapter discusses the modeling of small polarons in real materials, with a particular focus on the archetypal polaron material TiO2. After an introductory part, surveying the fundamental theoretical and experimental aspects of the physics of polarons, the chapter examines how to model small polarons using first principles schemes in order to predict, understand and interpret a variety of polaron properties in bulk phases and surfaces. Following the spirit of this handbook, different types of computational procedures and prescriptions are presented with specific instructions on the setup required to model polaron effects.Comment: 36 pages, 12 figure

Multicomponent Olivine Cathode for Lithium Rechargeable Batteries: A First-Principles Study

The in-depth study of the multicomponent effect Oil the structural and electrochemical properties of olivine cathodes is conducted using state-of-the-art first-principles calculations. The distribution of multiple transition metals in olivine structure alters local crystal structure and electronic structure, affecting its kinetic and thermodynamic properties. We find that local structure Change, Such its the reduced Jahn-Teller effect of Mn, significantly enhances both Li mobility and electron (polaron) conductivity when the redox Mn element neighbors Fe or Co. The unexpected one-phase Li insertion/extraction reaction of the multicomponent olivine cathode is explained with respect to the Multiple interactions of M/Li or M/vacancy (M = transition metals). The redox potential of each transition metal also could Shift its it result of charge redistribution and the relative energy change from the Multiple M/Li interactions. implications of multicomponent olivine as it useful Strategy for tailoring the electrochemical properties of olivine compounds are discussed for designing better-performing Li rechargeable batteries