Phonon bands in disordered systems with both mass and force constant defects: Isotopic mixed ice Ih

An isotopic mixed crystal study is conducted on the 226.5 cm^-1 phonon band in ice Ih. The result shows an amalgamation limit for this band with no significant clustering effect and indicates the absence of any isotope selectivity of the hydrogen bonds. The experimentally obtained self-energy when plotted against the mole fraction of the impurity (D₂O) yields a symmetric curve pointing out that the additional disorder in the mixed crystals is purely dynamic. The self-energy curve is fitted into a polynomial of the mole fraction of the impurity using regression analysis. The polynomial obtained reveals the importance of both the mass defect and the force constant defect. The result obtained is also shown to provide information regarding the dispersion of this phonon band.