Phonopy
A phonon-analysis package for harmonic and quasi-harmonic calculations, providing dispersions, densities of states and vibrational thermodynamic properties.
Where it fits
Converting converged forces or force constants into phonon and thermal results.
Limits and practical considerations
Usually needs an external force calculator; strong anharmonicity requires methods beyond a simple harmonic treatment.
Licensing and access
Open source under the New BSD licence; external force calculators retain their own terms.