### Resumen

The low-energy dielectric properties of CaC
_{6}
-a representative graphite intercalated compound (GIC)-were investigated by ab initio time-dependent density functional theory calculations with full inclusion of local field effects. The calculations predict the existence of several kinds of plasmons in CaC
_{6}
with energy below 10 eV. The mode with the largest energy is a conventional ''πp" mode strongly dispersing in the hexagonal basal plane and almost nondispersing in the perpendicular direction. In the 2.3-3 eV energy range, we find a long-lived intraband plasmon with negative (positive) dispersion with momentum transfer in (perpendicular to) the basal plane. In the 0-1.5 eV energy range, a mode with linear soundlike dispersion along all three high-symmetry directions is observed. All the three modes present strong anisotropy originated from the band structure. The physical origin of these excitation modes is discussed in terms of intra- and interband transitions. The crucial role of local field effects in the propagation of the two lowest-energy modes at large momentum transfers and in the determination of its dispersion over extended momentum-transfer region is analyzed.

Idioma original | Inglés |
---|---|

Número de artículo | 205135 |

Publicación | Physical Review B - Condensed Matter and Materials Physics |

Volumen | 85 |

N.º | 20 |

DOI | |

Estado | Publicada - 22 may 2012 |

Publicado de forma externa | Sí |

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_{6}.

*Physical Review B - Condensed Matter and Materials Physics*,

*85*(20), [205135]. https://doi.org/10.1103/PhysRevB.85.205135