Positive temperature-dependent thermal conductivity induced by wavelike phonons in complex Ag-based argyrodites
arxiv(2024)
摘要
The phonon transport mechanisms and the anomalous temperature-dependent
lattice thermal conductivities (kL) in Ag-based argyrodites have not been fully
understood. Herein, we systematically study the phonon thermal transport of
five Ag-based crystalline argyrodites Ag7PS6, Ag7AsS6, Ag8SnS6, Ag8GeS6 and
Ag9GaS6 utilizing perturbation theory and the unified theory thermal transport
model. Our results show that, as the complexity of the unit cell increases, the
proportion of the population terms falls while the coherence contributions
become more significant, leading to the relatively weak temperature-dependent
kL of Ag7PS6 and Ag7AsS6, while the more complex crystalline argyrodites,
Ag8SnS6, Ag8GeS6 and Ag9GaS6, exhibiting a glass-like behavior in their
temperature dependence of kL. We attribute the positive temperature-dependent
and ultralow kL of Ag8SnS6, Ag8GeS6 and Ag9GaS6 to the dominance of wavelike
phonons and the strong phonon broadening. Furthermore, using laser flash
measurements and the homogeneous non-equilibrium molecular dynamics simulations
based on accurate machine learning neuroevolution potentials, we provide
further evidence for the glass-like temperature-dependent kL of Ag8SnS6 and
Ag8GeS6.
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