Lattice collapse in mixed-valence samarium fulleride Sm(2.75)C(60) at high pressure |
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Authors: | Arvanitidis J Papagelis Konstantinos Margadonna Serena Prassides Kosmas |
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Institution: | Department of Chemistry, University of Sussex, Brighton, UK BN1 9QJ. |
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Abstract: | Sm(2.75)C(60) displays large negative thermal expansion behaviour in the temperature range 4.2-32 K at ambient pressure as a result of a quasi-continuous valence change from the larger Sm(2+) towards the smaller Sm(2.3+) ion. Here we use the powder synchrotron X-ray diffraction technique at ambient temperature and elevated pressures to study the compression behaviour in the pressure range 0-6 GPa. An abrupt hysteretic phase transition, accompanied by a dramatic volume decrease (approximately =6.0%) and a change in colour from black to golden was found at approximately =4 GPa induced by a sudden Sm valence transition from +2.3 towards +3. Such behaviour is typical of highly correlated Kondo insulators like SmS and makes Sm(2.75)C(60) the first known molecular-based member of this fascinating class of materials. |
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