| 1. |
- Aleksandrovskii, A. N., et al.
(författare)
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Thermal expansion of single-crystal fullerite C60 at helium temperatures
- 2000
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 26:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2–10 K). At temperatures below ~4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed.
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| 2. |
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| 3. |
- Wågberg, Thomas, et al.
(författare)
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2D polymerization and doping of fullerenes under pressure
- 2000
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Ingår i: High Pressure Research vol. 18. - : Gordon & Breach. ; 18:1-6, s. 139-143
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Konferensbidrag (refereegranskat)abstract
- Tetragonal polymeric C60 has been studied by Raman spectroscopy and other methods. Attempts have been made to transform samples from the tetragonal to the orthorhom-bic phase and vice versa. The results suggest that the transformation is direct with no intermediate stage with free molecules. Tetragonal C60 has also been intercalated by potassium metal.
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| 4. |
- Lebegue, Sebastien, et al.
(författare)
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Ab initio study of the electronic properties and Fermi surface of the uranium dipnictides
- 2006
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 73:4, s. 045119-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the uranium dipnictides UX2 (X=As, Sb, and Bi) is investigated by means of ab initio calculations based on density functional theory. The calculated Fermi surfaces are presented and compared to available experimental models obtained from de Haas-van Alphen experiments. In agreement with experiments they are found to have a significant two-dimensional character. Also, the change of the electronic properties through the series is discussed.
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| 5. |
- Soldatov, Alexander, et al.
(författare)
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Topochemical polymerization of C70 controlled by monomer crystal packing
- 2001
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Ingår i: Science. - : American Association for the Advanement of Science. - 0036-8075 .- 1095-9203. ; 293:5530, s. 680-683
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Tidskriftsartikel (refereegranskat)abstract
- Polymeric forms of C60 are now well known, but numerous attempts to obtain C70 in a polymeric state have yielded only dimers. Polymeric C70 has now been synthesized by treatment of hexagonally packed C70 single crystals under moderate hydrostatic pressure (2 gigapascals) at elevated temperature (300°C), which confirms predictions from our modeling of polymeric structures of C70. Single-crystal x-ray diffraction shows that the molecules are bridged into polymeric zigzag chains that extend along the c axis of the parent structure. Solid-state nuclear magnetic resonance and Raman data provide evidence for covalent chemical bonding between the C70 cages.
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| 6. |
- Wågberg, Thomas, et al.
(författare)
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Spectroscopic study of phase transformations between orthorhombic and tetragonal C60 polymers
- 2006
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Ingår i: The European Physical Journal B: Condensed Matter and Complex Systems. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 49:1, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed study of transformations between the orthorhombic and tetragonal polymeric states of C60. The transformations are characterised by Raman spectroscopy and X-ray diffraction. We show that the transformation from the orthorhombic (O) phase to the tetragonal (T) phase is very fast and our results indicate that the transformation goes via an intermediate dimer (D) state in a two-stage process, O↦D and, D↦T transformations, where the second process is slower than the first. On the other hand, the transformation from the tetragonal to the orthorhombic phase is significantly slower, indicating a high-energy threshold to break the polymer bonds at the temperatures used. The results also support earlier suggestions that the tetragonal phase contains disordered dimers that can be viewed as lattice defects in the formation of higher polymers.
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| 7. |
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| 8. |
- G.E. Grechnev,, et al.
(författare)
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Electronic structure and magnetic properties of Lithium manganese spinels
- 2003
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Ingår i: J.Magn. Magn. Matt.. ; 258, s. 287-289
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Tidskriftsartikel (refereegranskat)abstract
- Electronic and magnetic structures of the spinel-type lithium–manganese oxides LixMn2O4, x=0,0.5,1, are studied ab initio by employing a full-potential LMTO method. The effect of the orthorhombic distortion on electronic structure and magnetism of LiMn2O4 was investigated, and our calculations do not show a substantial charge ordering at the structural transition from the cubic spinel to the orthorhombic structure.
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| 9. |
- Joyce, J.J., et al.
(författare)
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Photoemission and the electronic structure of PuGaCo$_5$
- 2003
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Ingår i: Physical Review Letters. ; 91, s. 176401-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the first Pu-based superconductor PuCoGa5 is explored using photoelectron spectroscopy and a novel theoretical scheme. Exceptional agreement between calculation and experiment defines a path forward for understanding the electronic structure aspects of Pu-based materials. The photoemission results show two separate regions of 5f electron spectral intensity, one at the Fermi energy and another centered 1.2 eV below the Fermi level. The results for PuCoGa5 clearly indicate 5f electron behavior on the threshold between localized and itinerant. Comparisons to delta phase Pu metal show a broader framework for understanding the fundamental electronic properties of the Pu 5f levels in general within two configurations, one localized and one itinerant.
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| 10. |
- Vidya, R., et al.
(författare)
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Tailor-made electronic and magnetic properties in one-dimensional perovskite-like oxides
- 2003
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Ingår i: Physical Review Letters. ; 91, s. 186404-
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Tidskriftsartikel (refereegranskat)abstract
- Full-potential density-functional calculations show that the electronic structure of one-dimensional ferrimagnetic Ca3Co2O6 varies from metal to half metal to insulator as its magnetic ordering changes from the ferrimagnetic through the ferromagnetic to the paramagnetic state. The present Letter is the first to establish the occurrence of half metallicity in one-dimensional oxides. Moreover, the electronic and magnetic properties of this material can be tuned by substitution of Y for Ca, as shown by our detailed study on Ca3–xYxCo2O6 (x = 0, 0.3, 0.75, and 1). The Co ions are in two different valence states [Co4+ (low-spin) and Co2+ (high-spin)], and hence the occurrence of charge ordering in addition to spin ordering is established. For specific Y concentrations we predict a rarely seen combination of ferromagnetic and insulating behavior.
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