A NORMAL-MODE STUDY OF A POLYMER GLASS CONTAINING A CHROMOPHORE IMPURITY

We examine the vibrational density of states of atomistic models of po lypropylene glasses containing a single impurity molecule of s-tetrazi ne. We discuss existing methods and develop new ones to achieve signif icant data reduction and navigate through the complex spectrum of the normal modes of the glass. By calculating the participation ratio, the distribution of the kinetic energy of each mode on the atomic coordin ates, and a mode-proximity index to the solute it is possible to ident ify impurity-related, polymer-related, and mixed modes and assess thei r relative contributions to the vibrational density of states. Activat ion of specific modes using molecular dynamics allows the observation of anharmonicities in the doped glass, even at very low temperatures. (C) 1996 American Institute of Physics.