First-Principles Phonon Density of States of Graphite for Thermal Neutron Scattering Applications

Abstract

Abstract This study presents first-principles calculations of the phonon density of states (PhDOS) of graphite using density functional theory (DFT) within the local density approximation (LDA), as implemented in the Quantum ESPRESSO package. The calculated phonon spectrum exhibits characteristic vibrational features, including high-frequency in-plane optical modes reaching approximately 48 THz and low-frequency interlayer modes. The resulting PhDOS shows good agreement with the reference PhDOS derived from inelastic neutron scattering measurements, with minor discrepancies attributed to the harmonic approximation and finite-temperature effects. These results support the suitability of the LDA-based DFT approach for describing graphite lattice dynamics and provide a basis for constructing the thermal neutron scattering law S(α, β), thereby laying the groundwork for generating high-precision thermal scattering libraries for crystalline materials.