Inherent Anharmonicity of Harmonic Solids

Atomic vibrations, in the form of phonons, are foundational describing thermal behavior materials. The possible frequencies phonons materials governed by complex bonding between atoms, which is physically represented a spring-mass model that can account for interactions (spring forces) atoms (masses). lowest-order, harmonic , approximation only considers linear forces and thought incapable explaining phenomena like expansion conductivity, attributed to nonlinear, anharmonic interactions. Here, we show kinetic energy solid produces pressure much gas does. This vibrational or phonon naturally increases with temperature, as it does therefore results expansion. Because thermodynamically defines Grüneisen parameter γ typical metric anharmonicity, even will necessarily have some anharmonicity. A consequence this estimation ≈ 3 / 2 − 4 x 1 + where = v t l ratio transverse longitudinal speeds sound. We demonstrate immediate utility developing high-throughput estimate lattice conductivity comparable other state-of-the-art estimations. By linking properties explicitly, study provokes new ideas about fundamental nature while also providing basis material engineering design metrics.