Revealing the origin of strongly temperature-dependent lattice thermal conductivity in Cu2SnSe3
Year: 2026
Type: article
Abstract: Cu2SnSe3 exhibits exceptionally low lattice thermal conductivity (κL) and a nonclassical temperature dependence among ternary copper-based diamondoid compounds, yet the microscopic origins of these phonon behaviors remain poorly understood. In this work, we theoretically investigate the intrinsic phonon transport in Cu2SnSe3 by employing a two-channel thermal transport model that separates particle-like (κp) and coherent contributions (κc), while fully incorporating both three-phonon (3ph) and four-phonon (4ph) scattering processes. Our calculations show that κc is negligible at 300 K but becomes progressively more significant at elevated temperatures, while κp remains the dominant contributor to κL over the entire temperature range. 4ph scattering is identified as the primary factor driving the deviation from the classical T-1 dependence, yielding a temperature scaling of T-1.1 that closely matches the experimental T-1.2 behavior. This strong 4ph scattering originates from flat optical phonon modes in the 1.2-2.2 THz range, which provide an exceptionally large scattering phase space. The low κL (e.g., ~ 0.8 W m-1 K-1 at 773 K) of Cu2SnSe3 relative to other ternary copper-based diamondoid compounds is attributed to the asymmetric potential energy of Cu atoms, which induces large atomic displacement parameters and pronounced anharmonicity in the Cu-related low-frequency optical branches. Furthermore, qualitative analyses of cation disorder and anion substitution show that disorder leads to significant phonon broadening, while replacing Se with S hardens the acoustic branches and markedly shifts the optical modes upward. Our findings not only clarify the origins of the nonclassical temperature dependence and low κL in Cu2SnSe3, but also provide a general guideline for designing diamondoid thermoelectrics with intrinsically suppressed κL.
Source: Thermo-X
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7211891962