Unified approach for the calculation of force constants and accelerated convergence of atomic coordinates

A method which simultaneously computes the force-constant matrix (FCM) and relaxes the atomic coordinates to the ground state of a generic system is introduced. The method is based on the optimization of the FCM as the atomic coordinates evolve to their ground-state configuration, using the variations in atomic positions and forces from previous iterations as inputs. Striking accelerated convergence as compared to traditional methods is obtained, as well as accurate vibrational frequencies with no additional cost. © 1996 The American Physical Society.