  Following the approach of Yu, Singh, and Krakauer [Phys. Rev. B 43 (1991)
6411] we extended the linearized augmented plane wave code WIEN of Blaha,
Schwarz, and coworkers by the evaluation of forces. In this paper we describe
the approach, demonstrate the high accuracy of the force calculation, and use
them for an efficient geometry optimization of poly-atomic systems.

Materials Science;Materials Science