Validating first-principles phonon lifetimes via inelastic neutron scattering

Phonon lifetimes are a key component of quasiparticle theories transport; yet first-principles rarely directly compared with inelastic neutron scattering (INS) results. Existing comparisons show discrepancies even at temperatures where perturbation theory is expected to be reliable. In this paper, we demonstrate that the reciprocal space voxel ($q$ voxel), which finite region in required INS data analysis, must explicitly accounted for within order draw meaningful comparison. We accurate predictions peak widths function when accounting $q$ ${\mathrm{CaF}}_{2}$ and ${\mathrm{ThO}}_{2}$. Passing test implies high fidelity phonon interactions approximations used compute Green's function, serving as critical benchmark indicating other material properties should accurately predicted, thermal conductivity.