Calculation of the Lattice Frequencies of Alpha and Beta Oxygen.
MICHIGAN STATE UNIV EAST LANSING DEPT OF CHEMISTRY
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The optically active lattice frequencies of alpha- and beta-O2 have been calculated using an atom-atom Lennard-Jones potential, with and without the addition of an intermolecular quadrupole-quadrupole interaction. Both models predict frequencies reasonably close to those observed experimentally for alpha-O2, and support the assignment of the higher frequency librational mode to the torsion about the 2-fold axis in the crystal. Excellent agreement is obtained between the observed librational frequency and its temperature dependence in beta-O2 and the results calculated using the Lennard-Jones potential. If it is assumed that the molecules in beta-O2 may be tipped from the crystallographic c-axis, an increase in the tilt angle as the temperature is raised is predicted, which is consonant with the temperature dependence of the lattice constants for this phase. It is concluded that the Lennard-Jones atom-atom interaction is a satisfactory model for the potential function in solid oxygen, provided that the packing is such that electronic overlap effects are small. Author
- Atomic and Molecular Physics and Spectroscopy
- Solid State Physics