Effects of pressure and ambient species on the orientational ordering in solid C[sub 60]

Journal Article · Mon Feb 15 00:00:00 EST 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.47.4756· OSTI ID:6925547

Samara, G A; Hansen, L V; Assink, R A; Morosin, B; Schirber, J E; Loy, D ^[1]

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1. Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

The effects of hydrostatic pressure on the orientational ordering transition in solid C[sub 60] were investigated using helium, nitrogen, and a 50/50 (by volume) mixture of normal and isopentanes as pressure-transmitting media. The different observed responses in these media and for different samples, as well as some irreversible pressure cycling effects, have provided much insight into the ordering process. Highlights of the work include the following: (1) Lattice compression hinders the librational motion of the C[sub 60] molecules in the low-temperature simple cubic (sc) phase, thereby increasing [ital T][sub [ital c]] and stabilizing the sc phase; the effect is large; (2) the pressure dependence of [ital T][sub [ital c]], along with the accurately known volume change at the transition, yield 1.7 kcal/mole and 6.5 cal/K mole for the latent heat and discontinuous change in entropy, respectively, associated with the transition; (3) [ital T][sub [ital c]] and its pressure dependence are influenced by the presence of ambient species in the interstitial lattice sites. Helium appears to diffuse readily into the lattice, whereas N[sub 2] (and O[sub 2]) diffuse less rapidly and occupy octahedral sites; (4) a two-peak structure in differential thermal analysis spectra (also reported in specific-heat measurements) was observed and is believed to be due to the partial occupation of the octahedral sites by species such as N[sub 2] or O[sub 2]; (5) solid C[sub 60] reacts'' with pentane at pressures [ge] 14 kbar and temperatures [gt]475 K to yield an irreversible C[sub 60]/pentane complex similar to that obtained by the cocrystallization of C[sub 60] and normal pentane at 1 bar. These results are discussed in terms of proposed models.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6925547
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 47:8; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
FULLERENES
SORPTIVE PROPERTIES
HELIUM
ADSORPTION
NITROGEN
PENTANE
CHEMISORPTION
CRITICAL TEMPERATURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
DIFFUSION
INTERMOLECULAR FORCES
LATENT HEAT STORAGE
MOLECULAR STRUCTURE
PRESSURE DEPENDENCE
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0065-0273 K
VERY HIGH PRESSURE
ALKANES
CARBON
CHEMICAL REACTIONS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
ELEMENTS
ENERGY STORAGE
FLUIDS
GASES
HEAT STORAGE
HYDROCARBONS
NONMETALS
ORGANIC COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RARE GASES
SEPARATION PROCESSES
SORPTION
STORAGE
SURFACE PROPERTIES
TEMPERATURE RANGE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
360602* - Other Materials- Structure & Phase Studies