The vibrational states in a realistic model of amorphous iron

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Abstract
The vibrational density of states (DOS) of a realistic model structure of amorphous iron was calculated in two ways, using the equation of motion method and the recursion method, in which the quantitative disorder due to variations of interatomic force constants was found using the empirical potential of Pak and Doyama for alpha -Fe. It is shown that the vibrational DOS of amorphous iron has two peaks, an enhanced broad one on the low-frequency side and a fairly reduced one in the high-frequency side. The Debye parameters which characterise the whole spectrum and can be obtained by Mossbauer spectroscopy, were calculated. They are about 6% smaller than those values for the crystalline state ( alpha -Fe). The 'phonon' dispersion curves in amorphous iron were also computed from the wavenumber-dependent spectra both for longitudinal and transverse excitations. The authors observed a considerable softening of phonons associated with the metallic amorphous state.