Ne intercalated C{sub 60}: Diffusion kinetics
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
- Sandia National Laboratories, Albuquerque, New Mexico 87545 (United States)
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
{ital In situ} neutron powder-diffraction has been used to probe the Ne content and diffusion kinetics in C{sub 60} by monitoring the C{sub 60} lattice parameter vs time following step changes in applied Ne pressure. In the face-centered-cubic phase where the C{sub 60} molecules are freely rotating, diffusion is slower for higher Ne pressure. In the primitive cubic phase where the C{sub 60} molecules are orientationally ordered, the diffusion rate is slower and is essentially independent of pressure. These observations can be understood in terms of three unequal competing effects: (1) Increasing the external Ne pressure increases the driving force for diffusion; (2) compression of the C{sub 60} lattice slows diffusion with increasing pressure; and, the major one, (3) C{sub 60} molecular dynamics enables and enhances diffusion by a thermally activated {open_quotes}paddle wheel{close_quotes} effect. The activation energy for such Ne intercalated C{sub 60} reorientational hopping or rotation ({approximately}1500 K or 13 kJ/mole) is less than that in pure C{sub 60} ({approximately}2600 K or 22 kJ/mole), suggesting the Ne atoms act as {open_quotes}roller bearings.{close_quotes} {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 321525
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 9 Vol. 59; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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