On the spectral frequency distribution of translational vibrations in a face-centered cubic lattice of the C60 fullerite |
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Authors: | V P Mikhal’chenko V V Motskin |
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Institution: | (1) Institute of Thermoelectricity, National Academy of Sciences of Ukraine, Ministry of Education of Ukraine, Box 86, General Post Office, Chernovtsy, 58002, Ukraine |
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Abstract: | The spectral frequency distribution g(ω) of translational lattice vibrations in the face-centered cubic phase of the C60 fullerite at T = 300 K is calculated by the superposition method. The contribution from the translational vibrations to the heat capacity C V of the C60 fullerite and the x-ray characteristic temperature gJR entering into the exponent of the Debye-Waller factor are determined using the calculated frequency distribution g(ω). The results of the calculations are in good agreement with experimental data. It is noted that the librational and intramolecular lattice vibrations observed in the C60 fullerite do not contribute significantly to the temperature-induced decrease in the x-ray diffraction intensity at T = 300 K. The Grüneisen parameters γmod calculated from the x-ray diffraction data are consistent with the thermodynamic Grüneisen parameters γlat at temperatures T ≤ 80 K but substantially exceed those at T ≈ 300 K. New x-ray diffraction experiments are proposed for independently determining the anomalously large negative values of the parameter γ0, which is actually an orientational analog of the Grüneisen parameter. |
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