| Abstract | Based on thermodynamic principles, we derive expressions quantifying the
non-harmonic vibrational behavior of materials, which are rigorous yet easily
evaluated from experimentally available data for the thermal expansion
coefficient and the phonon density of states. These experimentally- derived
quantities are valuable to benchmark first-principles theoretical predictions
of harmonic and non-harmonic thermal behaviors using perturbation theory, ab
initio molecular-dynamics, or Monte-Carlo simulations. We illustrate this
analysis by computing the harmonic, dilational, and anharmonic contributions to
the entropy, internal energy, and free energy of elemental aluminum and the
ordered compound FeSi over a wide range of temperature. Results agree well with
previous data in the literature and provide an efficient approach to estimate
anharmonic effects in materials.
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