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Distortions of 4C60 Funding: Hungary OTKA T 034198, T 029931 US NSF-INT 9902050 studied by infrared spectroscopy G. Klupp, F. Borondics, G. Oszlányi, K. Kamarás, N. M. Nemes*, J. E. Fischer*, A. F. Hebard**, D. B. Tanner** Research Institute for Solid State Physics and Optics, P. O. Box 49, Budapest, H 1525, Hungary, email: [email protected] *Laboratory on the Research of the Stucture of Matter, University of Pennsylvania, Philadelphia, PA 19104, USA **Department of Physics, University of Florida, Gainesville, FL 32611, USA 600 K4C60, Rb4C60, Cs4C60 Na4C60 4 Na + C60 200 oC 10 d 1 regrind Na4C60 350 oC 10 d 1 regrind K4C60 IR Absorbance (a.u., baseline corrected) Preparation Mott-Jahn-Teller insulator [1] 4 K + C60 D2h [2] 350 oC 20 d 1 regrind 4 Rb + C60 Rb4C60 110 K K4C60 300 K 600 Detected molecular distortions: Cs4C60 neutron diffraction: D2h at 5 K, 293 K [3] K4C60 IR: D2h at 20-200 K, D3d / D5d at 300 K[4] [5] 6 Gu 7 Hu IR: 4 (T1u) 600 1300 1400 700 500 1400 Rb4C60 300 K 500 600 700 -1 1200 * / cm 600 1300 1200 Cs4C60 1300 1400 1300 1400 300 K 475 K 500 1400 700 96 K 600 700 -1 1200 * / cm Transition temperature: 200-220 K -1 Transition temperature: 270-290 K, 400 K Ci 1 Au (0 1) 12 Au (1 12) 15 Au (0 15) 24 Au (0 24) 35 Au (0 35) 87 (Au) A4C60 (A = Na, K, Rb, Cs) are air sensitive preparation and KBr pellet pressing in dry box measurements in dynamic vacuum -1 D2h 1 Au (0 0) 4 B1u + 4 B2u + 4 B3u (1 3) 5 B1u + 5 B2u + 5 B3u (0 3) 6 Au + 6 B1u + 6 B2u + 6 B3u (0 3) 14 Au + 7 B1u + 7 B2u + 7 B3u (0 3) 66(B1u, B2u, B3u) Sample characterization: XRD, Raman, IR purity > 95 % Rb4C60 K4C60 571 cm -1 K4C60 -1 200 250 300 Temperature (K) IR measurements: LN2 cooled cryostat Bruker IFS28 FT-IR transmittance measurements while warming up -1 1325 cm -1 1349 cm -1 1364 cm 647 cm -1 691 cm 150 200 250 100 300 Temperature (K) Ci 4Au + 4Au + 4Au Cs4C60 D2h 4B1u + 4B2u + 4B3u Rb4C60 D3d / D5d 4Eu + 4A2u K4C60 D3d / D5d 4Eu + 4A2u C60 Ih 4T1u every T1u split only T1u(3) & (4) splitting observed many strong new modes + 800 cm-1 mode (typical of single bonded fullerene polymers) covalent bonding strong distortion -1 200 300 646 cm -1 651 cm Cs4C60 572 cm -1 200 300 400 500 Temperature (K) 0.00 Temperature (K) 200 300 400 500 Temperature (K) IR(this work) D2h K4C60 T < 260-280K Rb4C60 T < 180-220 K D3d/D5d T > 260-280K T > 180-220 K D2h T < 400 K D3d/D5d T > 400K NMR [6,8] K4C60 axial rotation 250 K < T < 580 K hindered rotation T < 350 K quasi-isotropic rotation T > 350 K bct bco bct molecular axis nonparallel with c ordered anions molecular axis nonparallel with c Conclusion Na4C60 Cs4C60 Peak height (a.u.) Measurements Peak height (a.u.) Peak height (a.u.) Ci hindered rotation T < 250 K XRD [7,3] IR Absorbance (a.u., baseline corrected) 1300 87 K Transition temperature: 260-280 K Comparison at room temperature * / cm-1 1200 Cs4C60 Linewidth (cm-1) 5 F2u D3d 1 Au (0 0) 4 A2u + 4 Eu (1 2) 5 A2u + 5 Eu (0 2) 6 A1u + 6 A2u + 6 E2u (0 2) 7 A1u + 14 Eu (0 2) 44(A2u, Eu ) 1200 * / cm Linewidth (cm ) 4 T1u D5d 1 Au (0 0) 4 A2u + 4 E1u (1 2) 5 A2u + 5 E2u (0 1) 6 E1u + 6 E2u (0 1) 7 A1u + 7 E1u + 7 E2u (0 1) 26 (A2u, E1u) 350 10 d 1 regrind 4 Cs + C60 Correlation table Ih 1 Au oC 700 500 Linewidth (cm ) / 1400 -1 D3d 1300 Temperature dependence of Cs4C60 Peak Height (a.u.) / 1200 Peak height (a.u.) JTE: pn h Ih D5d 700 IR Absorbance (a.u., baseline corrected) Introduction Temperature dependence of Rb4C60 IR Absorbance (a.u., baseline corrected) Temperature dependence of K4C60 ordered anions@bco or merohedral disorder@bct static JTE staggered static distortion or dynamic JTE static JTE staggered static distortion or dynamic JTE potential field of counterions dominates molecular JTE dominates potential field of counterions dominates molecular JTE dominates Staggered static distortion few, weak new modes weak distortion References [1] M. Fabrizio and E. Tosatti, Phys. Rev. B 55, 13465 (1997). [2] C. C. Chancey and M. C. M. O’Brien, The Jahn-Teller effect in C60 and Other Icosahedral Complexes (Princeton University Press, Princeton, 1997). [3] P. Dahlke and M. J. Rosseinsky, J. Mater. Chem. 14, 1285 (2002). [4] K. Kamarás, G. Klupp, D. B. Tanner, A. F. Hebard, N. M. Nemes and J. E. Fischer, Phys. Rev. B 65, 052103 (2002). [5] G. Oszlányi, G. Baumgartner, G. Faigel and L. Forró, Phys. Rev. Lett. 78, 4438 (1997). [6] V. Brouet, H. Alloul, S. Garaj and L. Forró, Phys. Rev. B 66, 155122 (2002). [7] R. M. Fleming, M. J. Rosseinsky, A. P. Ramirez, D. W. Murphey, J. C. Tully, R. C. Haddon, T. Siegrist, R. Tycko, S. H. Glarum, P. Marsh, G. Dabbagh, S. M. Zahurak, A. V. Makhija and C. Hampton, Nature 352, 701 (1991). [8] C. Goze, F. Rachdi and M. Mehring, Phys. Rev. B 54, 5164 (1996).