Lattice dynamical calculations for the bulk agr;, bgr;, and ggr; phases of solid O2and for the monolayer agr; and bgr; phases have been made in the harmonic approximation. In the agr; and bgr; phases, atomhyphen;atom 6minus;12 potentials are employed. In the ggr; phase, effective potentials are used between molecular centers and only the translational lattice vibrations are calculated. It is found that Laufer and Leroirsquo;s potential parameters give twok=O frequencies at 42.7 and 43.6 cmminus;1in the bulk agr;hyphen;O2, and at 40.7 cmminus;1for the degeneratek=0 modes in the bgr; phase. The observed Raman lines for agr;hyphen;O2at 43 and 79 cmminus;1, which are both known to exhibit isotope shifts, are thus tentatively assigned to an accidentally degenerate line and a twohyphen;phonon band, respectively, In view of the possible contribution from anharmonic effects, the agreement of the calculation with experiment (48hyphen;51 cmminus;1) in bgr;hyphen;O2may be better than it seems. For the bulk ggr;hyphen;O2, a discrepancy is observed between the calculated elastic constants and those derived from Brillouin scattering experiments. This discrepancy may be due to the neglect of translationhyphen;rotation coupling. In the monolayer O2, Raman active modes at 28.3 and 40.6 cmminus;1for the agr; phase, and 31.9 cmminus;1for the bgr; phase are predicted.
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