## Abstract

Results of electronic structure calculations of C_{60} and M_{3}C_{60} (M = K, Rb, Cs) fcc crystals carried out by the full-potential linear muffin-tin orbital (LMTO) method are reported. Undoped C_{60} is found to be semiconducting with a direct gap between the fully occupied valence band and empty conduction band of 0.75 eV at the X-point. The Fermi level in M_{3}C_{60} falls on the half-occupied peak formed mainly by the 2p states of the closest carbon atoms with neighboring C_{60} molecules. Estimates of electron-phonon coupling using the crude rigid iron approximation give δ values of 0.51, 0.61 and 0.72 for K, Rb, and Cs doping, respectively. using an average phonon frequency of 1100 K the McMillan formula gives T_{c} values of 16 K for K_{3}C_{60}, 30K for Rb_{3}C_{60} and 47 K for Cs_{3}C_{60}. The calculated T_{c} values for K and Rb doping are in very good agreement with experiment and the predicted T_{c} value of Cs_{3}C_{60} is close to the value obtained by linear extrapolations based on the lattice constant. These are the first calculated results for δ and T_{c} and they strongly support the idea that BCS superconductivity is caused by the electron-phonon interaction and that T_{c} changes are caused by negative chemical pressures effects resulting in the increase of lattice constants in the K, Rb, and Cs series.

Original language | English |
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Pages (from-to) | 399-408 |

Number of pages | 10 |

Journal | Physica C: Superconductivity and its Applications |

Volume | 191 |

Issue number | 3-4 |

DOIs | |

Publication status | Published - Feb 15 1992 |

## ASJC Scopus subject areas

- Condensed Matter Physics