Effects of pressure and ambient species on the orientational ordering in solid C[sub 60]
- 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), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 47:8; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360602* -- Other Materials-- Structure & Phase Studies
ADSORPTION
ALKANES
CARBON
CHEMICAL REACTIONS
CHEMISORPTION
CRITICAL TEMPERATURE
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
DIFFUSION
ELEMENTS
ENERGY STORAGE
FLUIDS
FULLERENES
GASES
HEAT STORAGE
HELIUM
HYDROCARBONS
INTERMOLECULAR FORCES
LATENT HEAT STORAGE
MOLECULAR STRUCTURE
NITROGEN
NONMETALS
ORGANIC COMPOUNDS
PENTANE
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PRESSURE DEPENDENCE
RARE GASES
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
STORAGE
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VERY HIGH PRESSURE