Ab initiophonon dynamics of rhodium from a generalized supercell approach

We present a generalization of the supercell approach to the ab initio determination of the complete lattice dynamics. Combining force calculations for supercells of arbitrary shapes greatly increases the number of accessible interatomic force constants without the necessity to resort to large supercell sizes. The method allows a systematic a priori search for optimal supercell geometries as well as a posteriori improvements of calculations already performed. Its ability to efficiently handle systems with longer-range lattice interactions is demonstrated for the transition metal rhodium. The present approach has the potential to extend the applicability of the conceptually simple direct approach to the calculation of the complete phonon spectra for lattices with larger unit cells.