First Principles explanation of the positive Seebeck coefficient of lithium

Abstract

Lithium is one of the simplest metals, with negative charge carriers and a close reproduction of free electron dispersion. Experimentally, however, Li is one of a handful of elemental solids (along with Cu, Ag, Au etc.) where the sign of the Seebeck coefficient (S) is opposite to that of the carrier. This counterintuitive behavior still lacks a satisfactory interpretation. We calculate S fully from first-principles, within the framework of P.B. Allen's formulation of Boltzmann transport theory. Here it is crucial to avoid the constant relaxation time approximation, which gives a sign for S which is necessarily that of the carriers. Our calculated S are in excellent agreement with experimental data, up to the melting point. In comparison with another alkali metal Na, we demonstrate that within the simplest non-trivial model for the energy dependency of the electron lifetimes, the rapidly increasing density of states (DOS) across the Fermi energy is related to the sign of S in Li. The exceptional energy dependence of the DOS is beyond the free-electron model, as the dispersion is distorted by the Brillouin Zone edge, a stronger effect in Li than other Aliki metals. The electron lifetime dependency on energy is central, but the details of the electron-phonon interaction are found to be less important, contrary to what has been believed for several decades. Band engineering combined with the mechanism exposed here may open the door to new "ambipolar" thermoelectric materials, with a tunable sign for the thermopower even if either n- or p-type doping is impossible.

5 pages 4 figures

References in corpus (1)

• BoltzTraP. A code for calculating band-structure dependent quantities

Cited by in corpus (26)

• BoltzTraP2, a program for interpolating band structures and calculating semi-classical transport coefficients
• Electron-phonon interactions from first principles
• Towards predictive many-body calculations of phonon-limited carrier mobilities in semiconductors
• Calculating linear response functions for finite temperatures on the basis of the alloy analogy model
• Accelerated screening of thermoelectric materials by first-principles computations of electron-phonon scattering
• Phonon-limited electron mobility in Si, GaAs and GaP with exact treatment of dynamical quadrupoles
• Correlation effects on electron-phonon coupling in semiconductors: many-body theory along thermal lines
• Thermal conductivity and Lorenz ratio of metals at intermediate temperature: a first-principles analysis
• High-Performance Thermoelectric Oxides Based on Spinel Structure
• Large anisotropic thermal conductivity of intrinsically two-dimensional metallic oxide PdCoO${}_2$
• Electron-induced non-monotonic pressure dependence of the lattice thermal conductivity of θ-TaN
• Skewed Non-Fermi Liquids and the Seebeck Effect
• Anomalous thermoelectric transport phenomena from interband electron-phonon scattering
• Phase stability of Au-Li binary systems studied using neural network potential
• Impact of strain-induced electronic topological transition on the thermoelectric properties of PtCoO${}_2$ and PdCoO${}_2$
• Phonon limited thermoelectric transport in Pb
• Theory of thermoelectricity in Mg${}_3$Sb${}_2$ with an energy- and temperature-dependent relaxation time
• Variational Density Functional Perturbation Theory for Metals
• Positive Seebeck coefficient in highly doped La${}_{2-x}$Sr${}_x$CuO${}_4$ ($x$=0.33); its origin and implication
• Role of electronic excitation on the anomalous magnetism of elemental Copper
• What is measured when measuring a thermoelectric coefficient?
• Thermoelectric transport of strained CsK${}_2$Sb: The role of electron velocities and scattering within extended Fermi surfaces
• Symmetric Helmholtz Fermi-surface harmonics for an optimal representation of anisotropic quantities on the Fermi surface: Application to the electron-phonon problem
• Globally Optimal Band Structure for Thermoelectrics in Realistic Systems
• Wiedemann-Franz Law and Thermoelectric Inequalities: Effective ZT and Single-leg Efficiency Overestimation
• Valley-dependent electron-phonon scattering in thermoelectric semimetal Ta${}_2$PdSe${}_6$