Deciphering the phonon scattering mechanism and lattice thermal conductivity of La ₂ Zr ₂ O ₇ pyrochlores through point defect engineering: insights from molecular dynamics simulations with machine learning potentials

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pyrochlores are further classified into propagons, diffusons and locons based on the calculated phonon participation ratio (PR) and the Ioffe-Regel limit for each vibrational mode, revealing a broad distribution of wavelike vibrational states in defective structures. The lattice thermal conductivity and phonon quasi-particle lifetimes are calculated using both the perturbative linear Boltzmann transport equation (LBTE) and fully non-perturbative equilibrium molecular dynamics coupled with the Green-Kubo formula (EMD-GK) for temperature ranging from 300 K to 1500 K. The results reveal that some single- and mixed-type point defects including V48fO, Sn16cZr, Yb16cZr + Hf16cZr + V48fO and Yb16cZr + Sn16cZr + V48fO are the most prominent point defects in reducing phonon lifetimes, thus suppressing the lattice thermal conductivity and improving the performance of thermal barrier coatings (TBCs).