Far-infrared Vibrational Properties of Orthorhombic and Tetragonal C_60 Polymers
Abstract
We report high-resolution far-infrared transmittance measurements and quantum molecular dynamics (QMD) calculations of one-dimensional orthorhombic and two-dimensional tetragonal high-temperature and high-pressure (HTHP) C_60 polymers. The infrared spectra of both HTHP materials show no intermolecular modes but display complex intramolecular modes in our investigated frequency range (30-650 cm-1). The wide splitting and strong overlapping of the T_1u(1) and T_1u(2)-derived modes and some modes activated by symmetry reduction for the C_60 balls are assigned according to our QMD calculations, emphasizing the need for a strong perturbation model. We present a constituency analysis of mode parentage in each material. In addition, a comparison of the detailed far-infrared spectra and their assignments of the HTHP and alkali-doped orthorhombic C_60 polymers reveal that the charge effect, instead of the electron-phonon coupling, is the origin of the altered spectrum in the alkali-doped orthorhombic polymer. We will also discuss the defect modes of both orthorhombic and tetragonal C_60 polymers.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2001
- Bibcode:
- 2001APS..MARY15010Z