Gyula Faigel, Gábor Bortel, László Gránásy, Zoltán Jurek, Katalin Kamarás, Gyöngyi Klupp, Éva Kováts, Katalin Németh#, Gábor Oszlányi, Áron Pekker#, Tamás Pusztai, László Rátkai#, Attila Szállás, Zoltán Szekrényes#, Gyula Tóth, György Tegze, Miklós Tegze
Crystalline derivatives of fullerenes. — Fullerenes are closed shell carbon molecules. The most abundant among them is C60. The conjugated bond system makes C60 ideal precursor of ionic and covalent derivatives. In condensed state the rotation and the supramolecular interactions of the high-symmetry molecules enlarge the possibility of further structures. As a result of the above properties, fullerenes have unusually large number of solid state derivatives, like alkali metal salts, polymers and coctystals with a series of inorganic and organic molecules.
Lately we worked on fullerene based cocrystals. The study of these systems was extended to endohedral fullerenes. Several new, high-symmetry M3N@C80 compound was prepared, their structure was determined from powder and single crystal diffraction experiments and modeled in the framework of cohesion energy calculations. The solvent-free Sc3N@C80 crystal was prepared in 2 steps via thermal decomposition of its toluene solvate. This simple method may be applied to other hard-to-crystallize fullerenes. The new special double rotor-stator structure of the high stability Sc3N@C80-cubane was found to be face centered cubic in accordance to previous model calculations. More flexible rotor-stator system, of less stability is the cubic Sc3N@C80-mesitylene. These results were applied in preparation of analogous cocrystal structures of the potential MRI contrast agent, Gd3N@C80.
Infrared spectroscopy. — In prevoious years we mostly studied carbon based system, like carbon nanotubes, graphene, and hybrid materials based on these with other organic molecules. This year we concentrated on other type of materials.
We determined the chemical bonding and physical structure of adsorbed hydrogen on silicon and germanium surfaces. In some layers we detected the formation of blisters, a result important for possible hydrogen storage. We also characterized the surface of silicon carbide quantum dots by infrared spectroscopy and near-field infrared measurements on the nanoscale, and proved their potential for application in bioimaging.
Single molecule imaging. — Using the very short (10-100fs) and intense x-ray pulse of an X-ray Free Electron Laser, scattering on a single particle can give useful information on its structure before the sample would eventually be destroyed. Single particles are injected into the x-ray beam and scattering patterns of single particles are collected by 2D detectors and stored individually. One of the most challenging problems of single molecule imaging is how to assemble these noisy patterns of unknown orientations into a consistent single set of diffraction data. We have developed an efficient method to find the orientations of the noisy diffraction patterns. We have also shown that our method is able to select identical particles from a mixture and find their orientations simultaneously. Further, based on our molecular dynamics tool we showed that the orientation of molecules can also be determined from the measurement of fragment distribution. Our method allows
# Ph.D student
measurements of much smaller molecules then previously expected and also relaxes the requirements on the probe beam.
Figure1. Selection of different particles and determination of orientation of diffraction patterns. Left panel shows the block diagram of the algorithm. The upper right panel illustrates the convergence of the iteration. On the lower right panel the electron density of the NapAB protein molecule calculated from 100,000 simulated noisy diffraction patterns of the randomly oriented molecule overlaid on its ball-and-stick model. The model is shifted and rotated to the best fitting position.
Theory of phase transformations. — A simple dynamical density functional theory is used to investigate freezing of an undercooled liquid in the presence of a crystalline substrate.
We have reviewed the basic concepts and applications of the phase-field-crystal (PFC) method, which is one of the latest simulation methodologies in materials science for problems, where atomic- and microscales are tightly coupled. The PFC method operates on atomic length and diffusive time scales, and thus constitutes a computationally efficient alternative to molecular simulation methods
We have used the PFC theory to model the formation of eutectic dendrites in ternary systems;
a spectacular growth form discovered in 2010. We have shown that the two-phase and single phase dendrites have similar shapes. It has been found that the eutectic pattern, appearing on surface of the two-phase dendrites, may include concentric rings, and single- to multiarm
spirals, motifs of which thermal fluctuations choose. The number of spiral arms correlates with the tip radius and the kinetic anisotropy.
Grants and international cooperation
OTKA NK- 105691, Science in nanolaboratories (K. Kamarás 2013-2017)
ESA PECS Contract No. 4000104330/11/NL/KML: GRADECET-Phase-field modelling of columnar to equiaxed transition with fluid flow (L. Gránásy, 2011–2013).
Participation in EU FP7 NMP-2011-LARGE-5/280421 EXOMET – Physical processing of molten light alloys under the influence of external fields (L. Gránásy, 2012–2016)
ESA PECS Contract No. 4000104330/11/NL/KML: GRADECET – Phase-field modelling of columnar to equiaxed transition with fluid flow (L. Gránásy, 2011–2013).
OTKA K-81348. Ultrafast diffraction imaging of single particles (M. Tegze, 2010- 2014)
Publications
Articles
1. Frigeri C, Serényi M, Csik A, Szekrényes Zs, Kamarás K, Nasi L, Khánh NQ: Evolution of the structure and hydrogen bonding configuration in annealed hydrogenated a-Si/a-Ge multilayers and layers. APPL. SURF. SCI. 269: pp. 12-16. (2013)
2. Jagannathan A, Szallas A: Geometry fluctuations and Casimir effect in a quantum antiferromagnet. EUR. PHYS. J. B 86:(3) Paper 76. 5 p. (2013)
3. Jurek Z, Faigel G: Orienting single-molecule diffraction patterns from XFELs using heavy-metal explosion fragments. EUROPHYS. LETT. 101:(1) Paper 16007. 4 p. (2013) 4. Kamarás K, Klupp G, Matus P, Ganin AY, McLennan A, Rosseinsky MJ, Takabayashi Y,
McDonald MT, Prassides K: Mott localization in the correlated superconductor Cs3C 60 resulting from the molecular Jahn-Teller effect. J. PHYS.-CONF. SER. 428:(1) Paper 012002. 6 p. (2013)
5. Serényi M, Frigeri C, Szekrényes Zs, Kamarás K, Nasi L, Csik A, Khánh NQ: On the formation of blisters in annealed hydrogenated a-Si layers. NANOSCALE RES.
LETT. 8: Paper 84. 7 p. (2013)
6. Pusztai T, Rátkai L, Szállás A, Gránásy L: Spiraling eutectic dendrites. PHYS. REV.
E 87:(3) Paper 032401. 4 p. (2013)
7. Rátkai L, Kaban I, Wágner T, Kolář J, Valková S, Voleská I, Beuneu B, Jóvári P: Silver environment and covalent network rearrangement in GeS3-Ag glasses. J.
PHYS.-CONDENS. MATTER 25:(45) Paper 454210 7 p. (2013)
8. Tegze M, Bortel G: Selection and orientation of different particles in single particle imaging. J. STRUCT. BIOL. 183:(3) pp. 389-393. (2013)
Article in Hungarian
9. Szállás A, Rátkai L, Pusztai T, Gránásy L: Helikális mintázat eutektikus ötvözetekben.
(Helical patterns in eutectic alloys, in Hungarian). FIZIKAI SZEMLE 63:(10) pp. 333-337. (2013)
See also: S-D1, S-D2, S-G2