Geometry optimization of solids using delocalized internal coordinates

A new algorithm is presented that uses delocalized internal coordinates to optimize structures of periodic systems. The algorithm employs translational symmetry to construct the B matrix. It requires generation of all unique primitive internals in the unit cell. B is subsequently used to generate a set of delocalized internals as described in the earlier work by Pulay, Baker and coworkers for molecular systems. A detailed analysis of the algorithm for bulk Si is given, and the performance of the method in applications to surface reactions and zeolites is briefly mentioned.