Vibrational modes and phase transition of Si-Ge solid solution |
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Authors: | T Soma Y Kitani H-Matsuo Kagaya |
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Institution: | Department of Applied Physics and Mathematics, Mining College, Akita University, Akita 010, Japan |
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Abstract: | We present the simplified treatment where the lattice vibrations of Si or Ge atoms in the Si-Ge solid solution are replaced with that of pure Si or Ge crystal at lattice constants of the alloy. Considering the volume effect on the force constants of the pure constituent, we obtain the phonon dispersion curves of the local and band modes for Si0.91Ge0.09 and Si0.11Ge0.89 systems and the concentration x-dependence of the local and band modes frequencies in the Si1?xGex solid solutions. Then, from the calculation of the effective mode Grüneisen parameter γi for the average phonon modes in the Si1?xGex systems, we obtain the predominant correlation between TA mode Grüneisen parameter γXTA at the point X and the phase transition pressure Pt, and the softening of TA modes is related to the pressure-induced phase transition of the Si-Ge solid solution. |
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