which is related to the phonon DOS by a factor of (3N n a k B T ) -1 , where N is the number of lattice points and n a is the number of atoms per lattice point. Anharmonic properties can be derived by fitting the power spectra, G qλ , of individual phonon modes to Lorentzian functions. From this fitting, ω qλ is determined as the peak position, while the linewidth Γ qλ is determined as the fullwidth-at-half-maximum of each peak. Each G qλ is obtained from Equation and the velocity auto-correlation function of v qλ (t) is obtained from Equation . Phonon mode velocities v qλ (t) are derived from the normalmode-decomposition technique. Within this technique, v jl (t) are successively projected onto wave vectors q and phonon eigenvectors e qλ . DYNAPHOPY also allows the calculation of renormalised force constants from ω qλ values computed at commensurate q-points to interpolate ω qλ at incommensurate q-points and thus obtain the phonon dispersion.