Neutron scattering study of Na{sub 2}C{sub 60} in the pressure-temperature plane

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.60.10707· OSTI ID:692532

Yildirim, T; Neumann, D A ^[1]; Trevino, S F ^[1]; Fischer, J E ^[2]

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1. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
2. Materials Science Department and Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272 (United States)

Na{sub 2}C{sub 60} is the only known fulleride with divalent C{sub 60} and orientational order (Pa{bar 3} symmetry). We investigated the phase behavior of Na{sub 2}C{sub 60} for 0{lt}P{lt}4&hthinsp;kbar and 100&hthinsp;K{lt}T{lt}325&hthinsp;K using neutron scattering. Diffraction data indicate no change from Pa{bar 3} with applied pressure up to 4 kbar at temperatures below 200 K. In this phase, Na{sub 2}C{sub 60} is 37{percent} stiffer than pure C{sub 60} and 41{percent} softer than K{sub 3}C{sub 60}. However, for T{gt}200&hthinsp;K and P{gt}1&hthinsp;kbar, the structure is transformed into a low-symmetry distorted phase. Here the peaks at low Q are significantly broadened while the high Q peaks are almost completely smeared out. This transformation is reversible; releasing pressure above 200 K recovers the cubic Pa{bar 3} structure. {copyright} {ital 1999} {ital The American Physical Society}

• OSTI ID: 692532
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 15 Vol. 60; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
FULLERENES
INELASTIC SCATTERING
NEUTRON DIFFRACTION
ORIENTATION
PHASE TRANSFORMATIONS
POLYMERIZATION
PRESSURE DEPENDENCE
SODIUM COMPOUNDS
TEMPERATURE DEPENDENCE