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Showing papers by "Paolo Giannozzi published in 1994"


Journal ArticleDOI
TL;DR: In this paper, the vibrational frequencies and electric polarizability of the C60 molecule were calculated from first principles using density functional perturbation theory, and the results were in excellent agreement with existing experimental data, and they provided accurate predictions for those quantities (such as silent mode frequencies and vibrational eigenvectors) which are not easily accessible to experiments.
Abstract: The vibrational frequencies and electric polarizability of the C60 molecule, both in the gaseous and in the solid phases, are calculated from first principles using density‐functional perturbation theory. This method also allows us to obtain the infrared and Raman activities which had never been calculated before. Our results are in excellent agreement with existing experimental data, and they provide accurate predictions for those quantities (such as silent‐mode frequencies and vibrational eigenvectors) which are not easily accessible to experiments.

164 citations



Journal ArticleDOI
TL;DR: In this article, the structural and electronic properties of the fullides were analyzed using the Car-Parrinello method as well as standard local density approximation band structure calculations, and it was shown that metal clusters do not form but, like the potassium and rubidium fullerides, sodium intercalation gives rise to a conventional ionic compound.
Abstract: We calculate the structural and electronic properties of the ${\mathrm{Na}}_{6}$${\mathrm{C}}_{60}$ fulleride using the Car-Parrinello method as well as standard local density approximation band structure calculations. In contrast to previous claims we find that metal clusters do not form but, like the potassium and rubidium fullerides, sodium intercalation gives rise to a conventional ionic compound. Unlike the case of heavier alkali fullerides, a characteristic new kind of low-lying electron state appears that is not the ${\mathrm{C}}_{60}$ state. Effects of temperature on the electronic nature of the compound are discussed as well as consequences of these findings for higher fullerides.

18 citations


Posted Content
TL;DR: In this paper, the relative stability of different high-pressure phases of various Cesium Halides is studied from first principles and analyzed using the Landau theory of phase transitions using an acoustic phonon at the M point of the Brillouin zone.
Abstract: The relative stability of different high-pressure phases of various Cesium Halides is studied from first principles and analyzed using the Landau theory of phase transitions We present results for CsI, CsBr, and CsCl up to pressures of about 100 GPa A cubic-to-orthorhombic transition, driven by the softening of an acoustic phonon at the M point of the Brillouin zone, is competing with the cubic-to-tetragonal martensitic transition typical of these compounds The phonon softening takes place only in CsI and CsBr at a residual volume of 064, 052 respectively A cubic-to-tetragonal instability is found instead to occur at 054 for all the compounds considered here The orthorhombic phase is stable only in CsI, whereas it is taken over by the tetragonal one in the case of CsBr Our analysis reveals the essential role played by the phonon-strain coupling in stabilizing the orthorhombic phase and in making the corresponding transition first-order

16 citations