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تسجيل مستخدم جديدExcess Modes in the Vibrational Spectrum of Disordered Systems and the Boson Peak
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We study a disordered vibrational model system, where the spring constants k are chosen from a distribution P(k) ~ 1/k above a cut-off value k_min > 0. We can motivate this distribution by the presence of free volume in glassy materials. We show that the model system reproduces several important features of the boson peak in real glasses: (i) a low-frequency excess contribution to the Debye density of states, (ii) the hump of the specific heat c_V(T) including the power-law relation between height and position of the hump, and (iii) the transition to localized modes well above the boson peak frequency.
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We show that a {em vibrational instability} of the spectrum of weakly interacting quasi-local harmonic modes creates the maximum in the inelastic scattering intensity in glasses, the Boson peak. The instability, limited by anharmonicity, causes a com
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