Gyula Faigel, Gábor Bortel, László Gránásy, Zoltán Jurek, Katalin Kamarás, Gyöngyi Klupp, Bálint Korbuly#, Éva Kováts, Katalin Németh#, Gábor Oszlányi, Áron Pekker, Sándor Pekker, Frigyes Podmaniczky#, Tamás Pusztai, László Rátkai#, Zsolt Szekrényes#, Hajnalka Mária Tóháti#, Gyula Tóth, György Tegze, Miklós Tegze
The laboratory for advanced structural studies carries out research in three areas: carbon-based materials, the theory of phase transformations and X-ray-related methods. In the last year, we have reached significant results in the first two fields. We also carried out single-molecule x-ray imaging measurements at LCLS (Stanford); however, the evaluation of these measurements is quite involved and results are expected in the next year only.
Carbon based systems. — Lately, various carbon based materials have become the center of intensive research. Earlier, we concentrated on fullerenes and related compounds, whereas recently, metal organic framework materials (MOF), carbon nanotubes and nanotube-based hybrid systems have been our center of interest.
Metal-organic frameworks. — Metal-organic frameworks (MOFs) are high-porosity crystalline solids based on the coordination polymers of transition and rare-earth metals.
They are composed of two structural units: metal-containing clusters (secondary building units, SBUs) at the vertices and organic moieties (linkers) at the edges. The topologies of MOFs are controlled by the local symmetries and the functionalities of the SBUs and the linkers, resulting in the formation of 3D frameworks and also lower-dimensional structures.
MOFs are highly modular systems: more than one hundred types of SBUs and several thousand linkers can be combined to a huge number of individual structures with finely-tuned lattice parameters and properties. A spectacular characteristic of the family is the unusually low space filling: these materials have the highest inner surface area among all pore systems. The uniform shape and size of the ordered pores allow high rates of diffusion of gases. The supramolecular interactions with the guest molecules result in selective absorption. These properties make MOFs suitable hosts for effective storage of gases and for effective separation of mixtures of gases. Various chemical reactions can be performed in MOFs with significant topochemical control. The majority of the linkers are composed of rigid aromatic molecules with remarkable photophysical activities like fluorescence. Some SBUs have magnetic moments, making a group of MOFs to interesting molecular magnets.
Based on the above properties, MOFs and related architectures became the most intensively studied crystalline systems in material science in the last decade. This year we started to develop a new family of MOFs with Zn-based SBUs and cubane-dicarboxylate linkers. We successfully synthesized four new frameworks of different compositions, and determined their structures by single-crystal X-ray diffraction. The following new MOF structures formed: i): three interpenetrated networks with 4-connected, mononuclear SBUs;
ii): a 2D network with 4-connected, dinuclear SBUs (paddle-wheels); iii): a cubic network with 6-connected, tetranuclear SBUs; iv): a double-layered architecture with 7-connected, tetranuclear SBUs. The detailed characterization of the physical properties and the activation of the new MOFs are in progress. To study the supramolecular properties of
# Ph.D student
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MOFs, we also prepared various fullerene cocrystals of basic Zn-benzoate, the monomer precursor of the well known MOF-5.
Infrared spectroscopy on carbon-based systems. — A significant part of our research this year involved carbon nanotubes and nanotube-based hybrid systems. We studied the optical properties of separated metallic and semiconducting carbon nanotubes, and the mechanism of their sidewall functionalization reactions. Our most important results concerned carbon nanotubes filled with various small molecules, and the effect of the encapsulation on their fluorescent properties. Research on potential solar-cell materials involved surface modification of silicon quantum dots and nanowires of lead-methylamine iodide.
Theory of phase transformations. — We have investigated various aspects of crystalline freezing within atomistic and coarse-grained continuum models. Along this line, we studied the (precursor-mediated) homogeneous and heterogeneous nucleation of nanocrystals using a simple dynamical density functional theory, the phase-field crystal (PFC) model. It has been shown that the mismatch between the lattice constants of the nucleating crystal and the substrate plays a decisive role in determining the contact angle and nucleation barrier, which were found to be non-monotonic functions of the lattice mismatch.
We have shown that time-dependent studies are important, as investigations based on equilibrium properties often do not find all of the preferred nucleation pathways. We have investigated the structural aspects of the amorphous precursors in homogeneous nucleation mediated by an amorphous precursor (Fig. 1). Modelling of these phenomena is essential for designing materials on the basis of controlled nucleation and/or nano-patterning. The same atomistic continuum model has been used to evaluate the anisotropy of the body-centred cubic crystal-liquid interface as a function of orientation and temperature: The Euler–
Lagrange equation of the phase-field crystal model has been solved under appropriate boundary conditions for 18 orientations at various reduced temperatures. The orientation-dependent results were fitted with an eight-term Kubic harmonic series. The respective equilibrium (Wulff-) shapes vary with increasing reduced temperature from a nearly spherical shape to a polyhedral form (Fig. 2). We have investigated the anisotropy Figure 2. Wulff shapes computed from the
Kubic harmonic expressions fitted to 18 interface free energy values evaluated at each reduced temperature [ = 0.0, 0.1, 0.2, 0.3, 0.375, and 0.5 for panels (a)–(f), respectively].
Figure 1. Local order in the amorphous precursor assisting crystal nucleation in colloidal suspensions: fcc-, bcc-, hcp-like and liquid-like short range orders all appear.
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of the free energy for the crystal-liquid interface within a Ginzburg-Landau model, and have shown that remnant anisotropy exists at the critical point. We developed a nonlinear hydrodynamic theory of crystallization working on the atomic scale. The model recovers appropriate behaviour of acoustic phonons, the capillary wave spectrum, and steady-state growth with velocity inversely proportional to viscosity. Finally, we reviewed recent advances we made in using orientation-field-based phase-field approaches, and illustrated/discussed the possibility of making quantitative modelling of (a) complex polycrystalline growth morphologies and (b) the manipulation of the crystallization process (Fig. 3).
Figure 3. Orientation-field-based phase-field approaches to exotic growth morphologies: The results are presented in blocks: experiment is on the left, simulation(s) on the right. 1st row:
dumbbell shape (left) and “floral” (right) spherulites; 2nd row: ‘shish-kebab’ structure (left) of polymer disks on fullerene nanotube, and the effect of oscillating temperature (right); 3rd row: the effect of scratching on the crystallization of a polymer film.
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Grants
ESA PECS Contract No. 4000104330/11/NL/KML: GRADECET-Phase-field modelling of columnar to equiaxed transition with fluid flow (L. Gránásy, 2011–2014).
ESA PECS Contract No. 4000105034/11/NL/KML: MAGNEPHAS III – Modelling of growth and transformation kinetics (L. Gránásy, 2011–2014).
EU FP7 NMP-2011-LARGE-5/280421: EXOMET – Physical processing of molten light alloys under the influence of external fields (L. Gránásy, 2012–2016).
TÉT_12_FR-2-2014-0034: Phase-field modelling of polycrystalline and multi-phase solidification (T. Pusztai, 2014–2015).
OTKA NK- 105691, Science in nanolaboratories (K. Kamarás 2013-2017)
OTKA ANN-107580, Nanoscale investigation of molecular scaffolding (K. Kamarás 2013-2016)
OTKA K-81348, Ultrafast diffraction imaging of single particles (Tegze Miklós 2010- 2015).
International cooperation
Cooperation with colleagues at the École Polytechnique, Paris, France in the framework of the TÉT_12_FR-2-2014-0034 project (T. Pusztai, L. Gránásy, B. Korbuly, L. Rátkai).
Department of Chemistry, University of Nottingham, Prof. Andrei N. Khlobystov
Faculty of Physics, University of Vienna, Prof. Jannik C. Meyer (joint OTKA - FWF project) Department of Chemistry, Durham University, Prof. Kosmas Prassides
Publications
Articles
1. Bortel G, Kováts E, Oszlányi G, Pekker S: Crystal structure of the 4 + 2 cycloadduct of photooxidized anthracene and C60 fullerene. ACTA CRYSTALLOGR E, 70:(11) pp. 444-446. (2014)
2. Bortel G, Kováts E, Jakab E, Pekker S: Solvent-free Sc3N@C80-Ih and its precursor cocrystal with toluene. FULLER NANOTUB CAR N, 23:(6) pp. 557-565. (2014)
3. Botka B, Füstös ME, Tóháti HM, Németh K, Klupp G, Szekrényes Z, Kocsis D, Utczás M, Székely E, Váczi T, Tarczay G, Hackl R, Chamberlain TW, Khlobystov AN, Kamarás K:
Interactions and chemical transformations of coronene inside and outside carbon nanotubes. SMALL 10:(7) pp. 1369-1378. (2014)
4. Fogarassy Zs, Rümmeli MH, Gorantla S, Bachmatiuk A, Dobrik G, Kamarás K, Biró LP, Havancsák K, Lábár JL: Dominantly epitaxial growth of graphene on Ni (1 1 1)
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substrate. APPL SURF SCI, 314: pp. 490-499. (2014)
5. Granasy L, Toth GyI: Crystallization: Colloidal suspense. NATURE PHYSICS 10: pp. 12-13. (2014)
6. Granasy L, Podmaniczky F, Toth GI, Tegze G, Pusztai T: Heterogeneous nucleation of/on nanoparticles: a density functional study using the phase-field crystal model.
CHEM SOC REV, 43:(7) pp. 2159-2173. (2014)
7. Gránásy L, Rátkai L, Szállás A, Korbuly B, Tóth GyI, Környei L, Pusztai T: Phase-field modeling of polycrystalline solidification: from needle crystals to spherulites—A review. METALL MATER TRANS A, 45:(4) pp. 1694-1719. (2014)
8. Horváth E, Spina M, Szekrényes Z, Kamarás K, Gaal R, Gachet D, Forró L: Nanowires of methylammonium lead iodide (CH3NH3PbI3) prepared by low temperature solution-mediated crystallization. NANO LETT, 14:(12) pp. 6761-6766. (2014)
9. Kamarás K, Klupp G: Metallicity in fullerides. DALTON T. 43:(20) pp. 7366-7378. (2014) 10. Kocsis D, Kaptás D, Botos A, Pekker A, Kamarás K: Erratum to Ferrocene encapsulation in carbon nanotubes: Various methods of filling and investigation [Phys. Status Solidi B 248(11), 2512-2515 (2011)]. PHYS STATUS SOLIDI B, 251:(12) p. 2626. (2014)
11. Ludwig A, Kharicha A, Hölzl C, Domitner J, Wu M, Pusztai T: 3D Lattice Boltzmann flow simulations through dendritic mushy zones. ENG ANAL BOUND ELEM, 45: pp. 29-35.
(2014)
12. Maggini L, Füstös M-E, Chamberlain TW, Cebrián C, Natali M, Pietraszkiewicz M, Pietraszkiewicz O, Székely E, Kamarás K, De Cola L, Khlobystov AN, Bonifazi D:
Fullerene-driven encapsulation of a luminescent Eu(iii) complex in carbon nanotubes.
NANOSCALE 6:(5) pp. 2887-2894. (2014)
13. Podmaniczky F, Tóth GI, Pusztai T, Gránásy L: Free energy of the bcc-liquid interface and the Wulff shape as predicted by the phase-field crystal model. J CRYST GROWTH, 385:(1) pp. 148-153. (2014)
14. Szekrényes Zs, Somogyi B, Beke D, Károlyházy Gy, Balogh I, Kamarás K, Gali A:
Chemical transformation of carboxyl groups on the surface of silicon carbide quantum dots. J PHYS CHEM C, 118:(34) pp. 19995-20001. (2014)
15. Tóháti HM, Pekker Á, Pataki BÁ, Szekrényes Zs, Kamarás K: Bundle versus network conductivity of carbon nanotubes separated by type. EUR PHYS J B, 87:(6) Paper 126.
6 p. (2014)
16. Toth GI, Provatas N: Advanced Ginzburg-Landau theory of freezing: A density-functional approach. PHYS REV B, 90:(10) Paper 104101. 13 p. (2014)
17. Tóth GyI, Gránásy L, Tegze Gy: Nonlinear hydrodynamic theory of crystallization. J PHYS-CONDENS MATTER, 26:(5) Paper 055001. 10 p. (2014)
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18. Faigel G: A szerkezetkutatás új útjai (New ways of structure research, in Hungarian).
FIZIKAI SZEMLE 64:(10) pp. 354-357. (2014)
19. Németh G, Klupp Gy, Kováts É, Pekker S, Kamarás K: Kubán-fullerén kokristályok fázisátalakulásának infravörös spektroszkópiás vizsgálata (IR-spectroscopy study of the phase transitions of cubane-fullerene cocrystals, in Hungarian). FIZIKAI SZEMLE 64:(9) pp. 310-312. (2014)
20. Oszlányi G, Sütő A: Egy meglepően egyszerű algoritmus kristályszerkezetek meghatározására (A surprisingly simple algorithm for determining crystal structures).
FIZIKAI SZEMLE 64:(10) pp. 339-346. (2014) Book chapters
21. Granasy L, Pusztai T, Douglas JF: Insights into polymer crystallization from phase-field theory. In: Encyclopedia of Polymers and Composites. Ed.: Palsule S, Berlin;
Heidelberg: Springer-Verlag, 2014. Paper Ch 30. 35 p.
22. Pusztai T, Rátkai L, Szállás A, Gránásy L: Phase-field modeling of solidification in light-metal matrix nanocomposites. In: Magnesium Technology 2014 . Eds.: Alderman M, Manuel MV, Hort N, Neelameggham NR, New York: John Wiley and Sons, Inc., 2014.
pp. 455-459.
See also: S-D.30, S-D.31
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