Ordered low-temperature structure in K4C60 detected by infrared spectroscopy
نویسندگان
چکیده
Infrared spectra of a K4C60 single-phase thin film have been measured between room temperature and 20 K. At low temperatures, the two high-frequency T1u modes appear as triplets, indicating a static D2h crystal-field stabilized Jahn-Teller distortion of the C60 42 anions. The T1u(4) mode changes into a known doublet above 250 K, a pattern which could have three origins: a dynamic Jahn-Teller effect, static disorder between ‘‘staggered’’ anions, or a phase transition from an orientationally ordered phase to one where molecular motion is significant.
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