Application of generalized filter-diagonalization to extract instantaneous normal modes

In this paper, we apply the generalized filter-diagonalization (GFD) technique for extracting normal modes through correlation functions generated by molecular dynamics simulation. We test our method on a 256 argon particles system. Normal modes are calculated by the power spectrum of the velocity auto-correlation function, generalized filter-diagonalization, and direct diagonalization of the force matrix. The argon cluster provides a rigorous model for the generalized filter-diagonalization technique since the average separation between adjacent modes is less than 0.1 cm(-1). Excellent agreement was achieved even for normal modes that are separated by as little as similar to 0.01 cm(-1).