Enhancing the efficiency of thermoelectric materials relies heavily on reducing their lattice thermal conductivity. Since lowering the electronic contribution to heat transport negatively affects electrical performance, the focus shifts toward phonon engineering. Understanding phonon transport mechanisms is key to designing materials with reduced thermal conductivity using disorder and nanostructuring strategies.

We investigate phonon thermal transport in a silicon–germanium solid solution through classical molecular dynamics simulations coupled with harmonic lattice dynamics. Anharmonic effects, which are significant at elevated temperatures, are incorporated via the Green–Kubo approach to model lattice thermal conductivity. Additionally, phonon-projected density of states and mode-resolved mean free paths are analyzed.

The atomistic model accounts for mass contrast and random Ge substitution, enabling realistic disorder-induced phonon scattering. The vibrational spectra exhibit pronounced localization in high-frequency modes and broadening of spectral lines, indicating increased scattering. We observe that germanium atoms predominantly contribute to low-frequency phonon states, while silicon atoms dominate high-frequency dynamics. These effects collectively suppress heat transport by limiting phonon lifetimes and propagation lengths.

Our simulations demonstrate that introducing mass disorder and structural randomness leads to a substantial reduction in phonon-mediated heat conduction. This validates the approach of tuning phonon-scattering mechanisms as a practical route for improving thermoelectric performance. The results provide atomistic insight into how compositional disorder modifies vibrational behavior and thermal transport in SiGe-based alloys.