Low Temperature Physics: 34, 583 (2008); https://doi.org/10.1063/1.2957012 (9 pages)
Vibrational spectrum structure of two-component disordered chain at arbitrary compositions
M.A. Ivanov, V.S. Molodid, and Yu.V. Skripnik
Institute of Metal Physics, Kiev 03142, Ukraine
Received March 3, 2008
Using the Din method, the vibration spectrum of long disordered linear chains at arbitrary relations between concentrations of two components has been calculated and analyzed in detail within the isotopic approximation. Particular attention has been given to the case of light atoms predominance. It is shown that in the continuous spectrum region there appear large quantity of resonance peculiarities, which are responsible for by vibrational modes of short chains of light atoms with fixed ends. The width of the dips formed depends linearly on heavy atom concentration, while their depth is independent of concentration and defined by atom mass ratio. As this ratio increases, beginning with two, the dips transform into forbidden bands, the width of which depends linearly on heavy atom concentration too. New conditions of the opening of such zones have been found and analyzed. It is shown, that they cannot get inside the spectrum of heavy atom ideal chain. The step-by step transformation from the quasi-continuous spectrum structure with a series of peculiarities to the hierarchy structure of the local modes is traced.
PACS 63.22+m Phonons or vibrational states in low-dimensional structures and nanoscale materials;
Key words: impurity, disorder, chain, phonon, spectrum.