Role of structural relaxations and vibrational excitations in the high-frequency dynamics of liquids and glasses.

摘要: We present theoretical investigation on the high-frequency collective dynamics in liquids and glasses at microscopic length scales terahertz frequency region based mode-coupling theory for ideal liquid-glass transition. focus recently investigated issues from inelastic-x-ray-scattering computer-simulation studies dynamic structure factors longitudinal transversal current spectra: anomalous dispersion of sound velocity nature low-frequency excitation called boson peak. It will be discussed how mode interferes with other low-lying modes system. Thereby, we provide a systematic explanation sound-velocity systems--ranging high temperature liquid down to deep inside glass state--in terms contributions structural-relaxation processes vibrational excitations anomalous-oscillation peak (AOP). A possibility observing negative dispersion--the decrease upon increase wave number--is argued when is dominated by contribution dynamics. also show that excitation, observable both glass-state spectra same resonance frequency, manifestation AOP. As consequence presence AOP spectra, it predicted exhibits dispersion. These results are demonstrated model Lennard-Jones