Resolving Basis Dependence in Point-Defect Scattering Models for Thermal Conductivity in Multi-Sublattice Ceramics
Yinglu Tang (TU Delft - Aerospace Engineering)
Junsu Kim (University of Seoul)
Heechan Sang (University of Seoul)
Prakhar Jindal (TU Delft - Aerospace Engineering)
Botchu Jyoti (TU Delft - Aerospace Engineering)
Hyunsik Kim (University of Seoul)
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Abstract
Alloying is a widely used strategy for reducing lattice thermal conductivity through phonon scattering induced by mass and strain fluctuations. However, the evaluation of disorder-scattering parameters in multi-sublattice compounds remains inconsistent because both atomic- and unit-cell-based formulations are used in the literature. In this work, the origin of these discrepancies is systematically examined using ZrC and ZrB
2 as model systems. We show that the two approaches yield equivalent predictions only when a consistent basis is maintained throughout the calculation and the alloyed site has a degeneracy of unity. For compounds containing multiple sublattices or higher site degeneracy, the formulations diverge and can lead to substantially different estimates of alloying-induced phonon scattering. To address this issue, a generalized framework incorporating sublattice-selective disorder scattering is proposed. The formulation preserves basis consistency while accounting for the localized nature of disorder in complex compounds. The model is applied to W-doped ZrB
2 ceramics and compared with experimental thermal conductivity measurements. Improved agreement is obtained relative to conventional treatments. The proposed framework provides a physically consistent methodology for evaluating point-defect scattering in multi-sublattice solid solutions and enables more reliable prediction of lattice thermal conductivity in complex ceramic materials.
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