| 1. |
- Iwasiewicz-Wabnig, Agnieszka, et al.
(författare)
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Low-temperature optical studies of C60-cubane rotor-stator compound
- 2008
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Ingår i: Journal of Physics: Conference Series, vol. 100, part 5. - : Institute of Physics (IOP). ; , s. 052091-
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Konferensbidrag (refereegranskat)abstract
- We present here low-temperature Raman and photoluminescence spectra of the C60-cubane rotor-stator compound. We show the continuous evolution of Raman spectra between 77 K and room temperature, with no sharp transition visible at 140 K, the orientational ordering temperature. Low-temperature luminescence spectra of C60 in C60-cubane compound are found to be shifted and better resolved then spectra for pristine C60 at the corresponding temperatures, showing relatively weaker intermolecular interactions. In fact, the solid-state luminescence of C60-cubane is similar to free-molecule C60 luminescence spectra.
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| 2. |
- Iwasiewicz-Wabnig, Agnieszka, et al.
(författare)
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Polymerization of the rotor-stator compound C60-cubane under pressure.
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:2, s. 024114-
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Tidskriftsartikel (refereegranskat)abstract
- Cubane, C8H8, can be inserted into the octahedral voids of fullerene lattices to create a family of rotor-stator compounds. We have investigated the structural phase behavior of C60 center dot C8H8 by annealing a number of samples for up to 3 h at selected temperatures in the range 380-870 K under pressures up to 2 GPa. The high-pressure treated materials were then investigated under ambient conditions using Raman spectroscopy and x-ray diffraction. C60 center dot C8H8 is found to have at least five different structural phases depending on treatment conditions. In addition to the known cubic and orthorhombic structures observed at atmospheric pressure, we find two polymeric states with pseudocubic and pseudoorthorhombic structures, respectively, based on the two original lattices and created by heating in different pressure ranges. These materials are believed to be copolymers of C60 and decomposition products of cubane. In contrast to the polymeric states of C60 the present polymer structures are determined by the topology of the original lattices rather than by the molecular structure. Above 700 K we find a carbon-rich amorphous state created when the cubane finally decomposes, releasing its hydrogen content in the form of hydrocarbons.
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| 3. |
- Iwasiewicz-Wabnig, Agnieszka, et al.
(författare)
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Pressure-temperature phase diagram of the rotor-stator compound C60-cubane
- 2007
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 143:4-5, s. 208-212
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Tidskriftsartikel (refereegranskat)abstract
- When the rotor–stator compound C60·C8H8 is treated at temperatures above about 450 K under high-pressure conditions, fullerene-based copolymers are formed. Earlier results have shown the existence of two types of polymers, a “low-pressure” pseudo-cubic copolymer similar to that formed at atmospheric pressure, and a “high-pressure” phase tentatively identified as a pseudo-orthorhombic copolymer structurally based on the known low-temperature phase. In this communication we show that the reaction boundary between the polymers occurs at pressures near 1 GPa. From this result it follows that the slope of the cubic–orthorhombic phase line in the pristine material is 305 K GPa−1, significantly larger than the slope observed for the corresponding rotational transition in pure C60.
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| 4. |
- Sundqvist, Bertil, et al.
(författare)
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High pressure studies of the rotor-stator compound C60-cubane.
- 2007
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Ingår i: Materials Research at High Pressure. - Warrendale : Materials Research Society. - 9781558999442 ; , s. 0987-PP03
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Konferensbidrag (refereegranskat)abstract
- Insertion of cubane (C8H8) into the octahedral voids of the C60 lattice leads to the formation of an interesting rotor-stator compound which can be converted into a C60 co-polymer by heating. We have treated a number of C60C8H8 samples for up to 3 h each in the range 380-875 K under pressures up to 2 GPa. The resulting materials were investigated by Raman spectroscopy and X-ray diffraction. Depending on treatment conditions, at least five different structural phases can be found. In addition to the four structural phases observed at atmospheric pressure and different temperatures we find that a new polymeric state is created at pressures above 1 GPa, and we tentatively identify its structure as pseudo-orthorhombic. The cubic-orthorhombic phase transition line is found to have a slope of 295 K GPa-1, much larger than the slope of the fcc-sc line in pure C60.
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