ANHARMONIC VIBRATIONS VIA FILTER DIAGONALIZATION OF AB-INITIO DYNAMICS TRAJECTORIES

Filter diagonalization (Wall, M. R.; Neuhauser, D. J. Chem. Phys. 1995 , 102, 8011) is a new and efficient method for extracting frequencies and damping constants from a short-time segment of arty time-dependent signal, whether of quantum nature or not. In this letter, we will dem onstrate that filter diagonalization can be used to follow the anharmo nic vibrational dynamics of Si-6. Using the technique, we can locate ( resolve) the normal modes (including the widths) from even a very shor t-time correlation signal generated by ab initio molecular dynamics ca lculations. Our results show that filter diagonalization can reduce si gnificantly the necessary sampling time with an ab initio molecular si mulation and aid in understanding normal-mode dynamics for systems tha t are affected by anharmonicity.