Non-Fourier heat conduction predictions driven by device miniaturization require high-fidelity phonon properties. However, the accuracy of deterministic BTE solvers is constrained by the spectral fidelity of the phonon grouping scheme. Existing one-dimensional grouping strategies often struggle to simultaneously preserve accuracy in both the frequency and mean free path (MFP) domains, which degrades predictions in the quasi-ballistic–diffusive transition. Here we propose a dual-domain, multi-objective phonon grouping framework—Dual-Domain Optimization (DDO)—that leverages first-principles phonon properties and employs NSGA-II to jointly minimize the cumulative thermal conductivity spectral deviations in both domains, while constructing branch-level equivalent groups to conserve heat capacity and conductivity contributions. Validation on Si, GaN, Diamond, and BAs shows that, relative to the ShengBTE baseline, DDO maintains < 4% total-conductivity error in the frequency domain and markedly corrects MFP-domain deviations; for Diamond, the maximum equivalent MFP increases from 4 to 5 µm (single-domain grouping) to 17.16 µm (baseline 20.03 µm). The normalized Wasserstein distance decreases by a factor of 2–3 in Si and 7–9 in Diamond, accompanied by a concurrent reduction in the Davies–Bouldin Index (DBI). Coupling the reconstructed phonon properties with suppression functions yields in-plane/cross-plane that matches the baseline across all sizes, whereas traditional frequency-only grouping shows systematic overestimation in the quasi-ballistic regime. The method restores the distribution of length scales and mode-level representativeness without sacrificing frequency-domain fidelity, providing low-degree-of-freedom yet high-fidelity spectral inputs for deterministic BTE/DOM/LBM solvers and nano-/micro-device thermal design, and is highly reproducible and scalable. • Conventional uniform phonon groupings are shown to overestimate effective thermal conductivity. • Flexible grouping reassigns modes by phonon-property similarity beyond fixed bins. • Dual-domain NSGA-II optimization matches cumulative κ in frequency and MFP spaces. • Optimized spectra preserve key transport features for accurate non-Fourier heat.
Li et al. (Wed,) studied this question.