Boson peak in low-frequency Raman spectra of polymethylmethacrylate

The role of the local field, anharmonicity, and degree of disorder in the formation of the boson peak has been studied. The low-frequency Raman spectrum of a model polymethylmethacrylate crystal with disorder elements was calculated using the method of atom-atom potentials taking into account the effect of local fields on the spectrum. The calculations were carried out for a crystal containing rigid molecules of an isotactic polymethylmethacrylate oligomer and for a structure with flexible molecules.