Equations of state of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Rb</mml:mi></mml:mrow><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">C</mml:mi><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:mrow></mml:math>(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mrow><mml:mi>x</mml:mi><mml:mo>=</mml:mo><mml:mn>3</mml:mn></mml:mrow></m

Sabouri-Dodaran, A. A.; Marangolo, M.; Bellin, Christophe; Mauri, Francesco; Fiquet, G.; Loupias, G.; Mézouar, M.; Crichton, Wilson A.; Hérold, Claire; Rachdi, F.; Rabii, S.

doi:10.1103/physrevb.70.174114

Cited by 15 publications

(21 citation statements)

References 35 publications

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“…The smaller crystal field is a consequence of the larger free volume in the A 4 C 60 compounds compared to A 3 C 60 or A 6 C 60 . 36 The mean amplitude of the libration can also be calculated within the harmonic approximation from the librational energy via 9. ͑Color online͒ ͑a͒ Fixed momentum transfer scans of K 4 C 60 at 100, 200, and 300 K at Q = 5.5 Å −1 .…”

Section: Librationsmentioning

confidence: 99%

Static and dynamic Jahn-Teller effect in the alkali metal fulleride saltsA4C60(A=K,<

et al. 2006

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We report the temperature dependent mid-and near-infrared spectra of K 4 C 60 , Rb 4 C 60 , and Cs 4 C 60 . The splitting of the vibrational and electronic transitions indicates a molecular symmetry change of C 60 4− which brings the fulleride anion from D 2h to either a D 3d or a D 5d distortion. In contrast to Cs 4 C 60 , low temperature neutron diffraction measurements did not reveal a structural phase transition in either K 4 C 60 and Rb 4 C 60 . This proves that the molecular transition is driven by the molecular Jahn-Teller effect, which overrides the distorting potential field of the surrounding cations at high temperature. In K 4 C 60 and Rb 4 C 60 we suggest a transition from a static to a dynamic Jahn-Teller state without changing the average structure. We studied the librations of these two fullerides by temperature dependent inelastic neutron scattering and conclude that both pseudorotation and jump reorientation are present in the dynamic Jahn-Teller state.

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Section: Librationsmentioning

confidence: 99%

Static and dynamic Jahn-Teller effect in the alkali metal fulleride saltsA4C60(A=K,<

et al. 2006

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“…13, and references therein͒. External pressure changes the thermodynamic energy levels of alkali fullerides [15][16][17][18][19][20][21] and pressure studies are therefore very powerful tools to explore structural phase transitions. The narrow-gap insulator A 4 C 60 ͑A =K,Rb͒ is an especially interesting system for which a number of high-pressure studies have been reported, but where the data and interpretations by different groups are contradictory.…”

mentioning

confidence: 99%

“…The narrow-gap insulator A 4 C 60 ͑A =K,Rb͒ is an especially interesting system for which a number of high-pressure studies have been reported, but where the data and interpretations by different groups are contradictory. 11,[16][17][18][19] Sabouri-Dodaran et al 16 reported an abrupt jump in the compressibility of Rb 4 C 60 between 0.5 GPa and 0.8 GPa, attributed to a phase transition preserving the tetragonal symmetry. A later study suggests instead a transition from tetragonal to orthorhombic symmetry above 0.4 GPa, accompanied by an orientational disorder-order transition for the C 60 molecules.…”

mentioning

confidence: 99%

Reversible pressure-driven nanoscale phase separation inRb4C60

2009

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We present Raman spectra for Rb 4 C 60 at pressures up to 13 GPa. Above 1 GPa we observe a phase separation of Rb 4 C 60 into Rb 6 C 60 and Rb 3 C 60 , identified by a splitting of the A g ͑2͒ mode and the appearance of characteristic Raman modes of the daughter phases. Remarkably, the phase separation is completely reversible and the sample returns to a homogeneous Rb 4 C 60 phase after pressure release. The reversibility of the phase separation suggests that the structural change is associated with small displacements of Rb ions in the unit cell, giving local differences in the charge state of the C 60 molecules. The pressure dependence of the Raman shifts agrees well with earlier measurements. Our observation of a reversible phase separation explains several peculiar results reported earlier for Rb 4 C 60 .

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“…The pressure-dependent XRD measurements by Huq and Stephens [6] and Sabouri et al [5] give the unit cell volume change V (P) in the pressure range which is of interest here. By assuming that α is pressure independent, the highfrequency dielectric permittivity was obtained and is shown with increasing pressure in Fig.…”

Section: Original Papermentioning

confidence: 99%

Hints for the metallic phase in Rb₄C₆₀ under pressure

Francis

Kuntscher

2014

Physica Status Solidi (b)

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The alkali fulleride Rb4C60 was investigated by infrared spectroscopy under high pressure, to study the vibrational and electronic excitations. The material exhibits a bad metal behavior in the measured pressure range (0.8–8 GPa). With increasing pressure the Drude term in the far‐infrared region increases, which signals an increasing metallic character. By following the optical excitations under pressure, we could attribute the underlying mechanism of the pressure‐induced insulator‐to‐metal transition in Rb4C60 to the closing of the charge gap, and the nanoscale phase separation scenario discussed in the literature seems to be unlikely.

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Equations of state ofRbxC60(x=3

Cited by 15 publications

References 35 publications

Static and dynamic Jahn-Teller effect in the alkali metal fulleride saltsA4C60(A=K,<

Static and dynamic Jahn-Teller effect in the alkali metal fulleride saltsA4C60(A=K,<

Reversible pressure-driven nanoscale phase separation inRb4C60

Hints for the metallic phase in Rb₄C₆₀ under pressure

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Equations of state ofRbxC60(x=3

Cited by 15 publications

References 35 publications

Static and dynamic Jahn-Teller effect in the alkali metal fulleride saltsA4C60(A=K,<

Static and dynamic Jahn-Teller effect in the alkali metal fulleride saltsA4C60(A=K,<

Reversible pressure-driven nanoscale phase separation inRb4C60

Hints for the metallic phase in Rb4C60 under pressure

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Hints for the metallic phase in Rb₄C₆₀ under pressure