When: May 7, 15:00

Different contributions to thermal conductivity in metals through atomistic simulations

Thermal conductivity in metals arises from multiple energy transport channels, including the dominant electronic contribution, lattice vibrations (phonons), and, in the case of magnetic materials, spin excitations (magnons). In this work, we use molecular dynamics (MD) simulations to investigate the lattice and the spin contributions to thermal conductivity of a ferromagnetic body-centred cubic, bcc-Fe, in a spin–lattice dynamics framework. We evaluate the thermal conductivity using two different approaches: equilibrium MD (EMD) and non-equilibrium MD (NEMD). The Green–Kubo formula, which relates the autocorrelation function of the heat flux to the thermal conductivity, is used in the EMD approach, while Fourier’s law is used in NEMD. The comparison of the conductivities obtained in the different approaches allows us to assess the accuracy and predictive power of the MD methods. All atomistic simulations are performed using the LAMMPS[1] open source code, which deals with not only the atomic positions, but also with the classical Heisenberg spin dynamics.

At room temperature, the computed lattice conductivity is κ_lat ≃ 13 W/m·K; the spin thermal conductivty  κ_spin ≃ 8 W/m·K, to be compared with an electronic conductivity κel ≃ 70 W/m·K as obtained by Wiedemann-Franz law applied to experimental data [2].

Reference:

1. Thompson, A. P., Aktulga, H. M., Berger, R., Bolintineanu, D. S., Brown, W. M., Crozier, P. S., … & Plimpton, S. J. (2022). LAMMPS-a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales. Computer physics communications, 271, 108171.
2. Fulkerson, W., Moore, J. P., & McElroy, D. L. (1966). Comparison of the thermal conductivity, electrical resistivity, and Seebeck coefficient of a high‐purity iron and an Armco iron to 1000° C. Journal of Applied Physics, 37(7), 2639-2653.