Instantaneous normal mode analysis of liquid HF

We present an instantaneous normal mode analysis of liquid HF aimed at clar ifying the origin of peculiar dynamical properties which are supposed to st em from the un arrangement of molecules in a linear hydrogen-bonded network . The present study shows that this approach is a unique tool for the under standing of the spectral features revealed in the analysis of both single m olecule and collective quantities. For the system under investigation, we d emonstrate the relevance of hydrogen-bonding "stretching" and fast libratio nal motion in the interpretation of these features.