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2015 Fall

Characterization of materials by experiments and computing


High Pressure as a Tool to Design & Synthesize new High Tc Superconductor, Hard Materials & Multifunctional Oxides

The relation between electronic structure and the crystallographic atomic arrangement is one of the fundamental questions in condensed matter physics and inorganic chemistry. Since the discovery of the atomic nature of matter and its periodic structure, this has remained as one of the main questions regarding the very foundation of solid systems. Needless to say this has also bearings on physical and chemical properties of matter, where again the relation between structure and performance is of direct interest.




High-pressure science is a fast developing new field in condensed matter physics and may even be regarded as the exploration of an entirely new dimension. This is to a large portion of course due to the development of the diamond anvil cell (DAC) technique with which one can easily control the pressure for systems of interest in the range of several mega bars and due to increasingly sophisticated synchrotron facilities to observe some of the drastic changes effected in the physical properties. With pressure, we can tune electronic, magnetic, structural and vibrational properties of condensed matter for a wide range of applications. ``Inert gases'' cease to be noble and inert, and can form stoichiometric compounds; likewise, normally unreactive transition metals can form alloys with alkali metals; silicate tetrahedral frameworks, the basis of rock-forming minerals, are destroyed and replaced by silicate octahedra; carbon rings, basic structural units of polymer and organic chemistry, become unstable and are replaced by diamond-like structures. High-pressure research has been predicted to ultimately even lead to the establishment of a new Periodic Table, one which has the same elements but completely redefined physical and chemical behaviors at megabar pressures. In this sense, the field of high pressure could indeed establish itself as a dimension in physical science on a par with temperature (low- and high-temperature physics) and composition (chemistry and materials science). First of all the exploration of the megabar pressure range is highly interesting by itself, where new physics and chemistry can be expected. Second, the general problem about the equation-of-state in this pressure range is highly significant for a vast number of materials. The underlying mechanisms determining the geometrical arrangement of atoms can be elucidated by the study of matter at extreme conditions, probing a new range of electron densities. One example where high pressure can play important role, for example for search of new high Tc superconductors or Hard materials. Materials under pressure change their forms and the superconducting state of a material is strongly linked to these structural phase transition. Pressure enhances electron-phonon interactions and the corresponding critical temperature (Tc). An important byproduct from this meeting at EMRS (September, 2015) could lead to an improved understanding and performance of materials at ambient and extreme conditions.


Hot topics to be covered by the symposium


  • Topological Insulators
  • Hard Materials ( Carbon based materials)
  • Hydrogen densed materials
  • Phase Change materials
  • Functional Oxides
  • Dilute magnetic semiconductors
  • Data Driven discovery


Tentative list of invited speakers


  • H.K. Mao, Washington, USA & Shanghai, China 
  • C.Q. JIN, IOPCAS, China
  • T. Cui, Jilin University, China
  • Y.S. Zhao, UNLV, USA
  • H.Z. Liu, Harbin Institute of Technology, China
  • Y.J. Tian, Yanshan University, China
  • H.Q. Lin, Center for Computaion Physics, Beijing, China
  • A. Zaoui, University of Science & Technology, Lille, France
  • L.S. Dubrovinsky, University Bayreuth, Germany
  • S.C. Gupta, BARC, India
  • Artem Oganov, State University of New York, Stony Brook, USA
  • John Tse, Univ. of University of Saskatchewan, Canada
  • K. Aoki, IMR, Tohoku, Japan
  • T. Irifune, Ehime, Japan
  • Udomsilp Pinsook, Chulalongkorn University, Thailand
  • J.E. Lowther, Univ. of Wits, South Africa


Tentative list of scientific committee members


  • B.Johansson, KTH, Stockholm, Sweden
  • S.M.Sharma, Bhabha Atomic Research Center (BARC, India)
  • H.D.Hochheimer, Colorado State University, USA

No abstract for this day

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Authors : Iryna Gnatenko, Igor Andreiev, Serhii Lysovenko, Volodymyr Bondarenko, Matvey Loshak, Oleksandr Shulzhenko
Affiliations : V.Bakul Institute for superhard materials of NAS of Ukraine

Resume : The study was conducted to establish the behavior of the material at high pressure. In this work was used cemented carbide WC-6% by weight of the alloy Co. Samples was sintered in a vacuum at a temperature of 1450 °C, sintering duration was 1 hour. The average grain size of sintered cemented carbides was 1.4 microns, porosity 0,02% by volume, ƞ - phase missing. Later, the resulting material was subjected to high pressure processing in high-pressure equipment of type "toroid". The pressure of the processing was 7.5 GPa, temperature 1700 °C, 1 min exposure. After processing the samples were investigated using X-ray and metallographic analyzes. It was found that the average grain size of the alloy and the total porosity has not changed. The intensity etching by Murakami's reagent of cemented carbides changed That is, after applying of pressure was fixed decreasing corrosion resistance of cemented carbide. In determining the phase composition of samples subjected to processing pressure, the formation of new phases no installed. During the measurement of density, coercive force and physical and mechanical characteristics of the samples was set changes. After the application of high-pressure to the sample alloy WC-6% by weight Co decreased the density from 14.84 g/cm3 to 14.66 g/cm3. Coercive force and power during compression decreases too. To explain the decline of physical and mechanical properties of carbide after the application of pressure will need to further studies samples.

Authors : M. Werwiński, W.L. Malinowski, P. Leśniak, A. Szczeszak*, S. Lis*, and A. Szajek
Affiliations : Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland *A. Mickiewicz University, Faculty of Chemistry, Department of Rare Earths, Umultowska 89b, 61-614 Poznań, Poland

Resume : Orthovanadates have recently emerged as promising optical materials for birefringent solid-state laser applications [1], cathodoluminescent materials, thermophosphors, or scintillators [2]. At ambient conditions YVO4 crystallizes in zircon-type structure and transforms under pressure into scheelite-type phase. The change of energy band gap with pressure has been investigated theoretically. The fully relativistic calculations have been carried out with exchange-correlation potential in GGA U form (generalized gradient approximation including on-site Coulomb energies). Full-Potential Local-Orbital Minimum-Basis Scheme (FPLO-14) has been employed [3]. The failure of the band gap predictions within the pure GGA comes from not sufficient treatment of the strong correlations. On-site Coulomb potential (GGA U) applied to oxygen O(2p) orbitals provides a crucial insight into the width of the band gap calculated for the zircon-type structure. Also the influence of the potentials U on the remaining V(3d) and Y(4d) valence bands has been studied. The lattice parameters measured under pressure have been employed [4] to calculate evolution of XPS photoemission spectra. [1] W. Ryba-Romanowski, Cryst. Res. Technol. 38, (2003) 225. [2] D. F. Mullica et al., Inorg. Chim. Acta 248 (1996) 85. [3] K. Koepernik, H. Eschrig, Phys. Rev. B 59 (1999) 1743. [4] X. Wang et al., Phys. Rev. B 70 (2004) 064109. Work supported by the National Science Centre (Poland) grant: DEC-2011/01/B/ST3/02212 .

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Authors : Yoshiya Uwatoko
Affiliations : Institute for Solid State Physics, The University of Tokyo, Kashiwanoha, Kashiwa, 277-8581, Japan

Resume : In strongly correlated electron systems, unusual superconductivity has been studied. Recently, a number of pressure induced superconductors have been found in the vicinity of a ordered phase of a quantum critical point (QCP). In the 4f magnetic ordered systems, the magnetic quantum criticality arises by tuning the competition between the RKKY interaction and the Kondo effect. While the coupling between spin and orbital degrees of freedom is unavoidable in transition metal systems, f-electron systems may provide an ideal nonmagnetic state where orbitals are the only active degree of freedom. One such nonmagnetic state can be found in the cubic 4f2 systems such as Pr based compounds when the crystal electric field (CEF) stabilizes the so-called G3 doublet state with an electric quadrupole moment. The orbital degree of freedom takes the form of the electric quadrupole moment, which may form a variety of electric ground states such as the quadrupolar order through indirect RKKY-type interaction. Its hybridization with a conduction electron may also induce a nonmagnetic form of the Kondo effect that quenches the quadrupolar moment and leads to an anomalous metallic state. Without the disadvantage of introducing disorder, pressure is one of the cleanest tuning parameters. The PrTr2Al20 (Tr=Ti and V), which crystallizes in a cubic structure [1], has demonstrated that the interplay of the quadrupole order and Kondo effect [2]. Here we present the discovery of the pressure-induced heavy fermion superconductivity in PrTi2Al20. The PrTi2Al20 single crystals were grown by the Al-flux method as described in the literature. We have used a cubic anvil and modified Bridgman anvil cell with in-situ pressure tuning in a 3He and dilution refrigerator to the study of the electrical phenomena. Electrical resistivity, AC susceptibility and AC calorimetric were measured on high quality single crystals of PrTi2Al20. A magnetic field was applied to determine the upper critical field HC2, as well as the effect of magnetic field on the under pressure. At ambient pressures we find a superconducting phase below 0.2 K which is suppressed by an extremely small field [2]. We confirm the increase of TQ at low pressure, and the increases of superconductivity over about 6 GPa, with an initially rather small HC2, which increases significantly as TQ starts to decrease, as found in the previous study. We find that at higher pressures the decrease of TQ continues, and is accompanied by a further enhancement of HC2, reaching over 5 Tesla, more than double the theoretical paramagnetic limit. We found that the transition temperature, Tc, and the effective mass, m*, associated with the superconductivity are dramatically enhanced as the system approaches the putative quantum critical point of the orbital order. Our experiment indicates that the strong orbital fluctuations may provide a nonmagnetic glue for Cooper pairing [3]. [1] S. Niemann, W. Jeitschko, J. Sol. State Chem. 114, 337–341 (1995). [2] A. Sakai et al., J. Phys. Soc. Jpn. 81, 083702 (2012). [3] K. Matsubayashi et al., Phys. Rev. Lett 109, 187004 (2012)

Authors : N.L. Saini
Affiliations : Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 2, 00185 Roma, Italy

Resume : Among transition metal dichalcogenides, IrTe2 is a good example in which superconductivity appears due to suppression of first-order structural phase transition. Here, we have studied nanoscale structure of Ir1-xPtxTe2 to understand structural phase transition and appearance of superconductivity in this system. X-ray absorption measurements reveal Ir-Ir dimerization and appearance of longer Ir-Te bondlengths below the structural phase transition temperature in IrTe2. The local structure also reveals substantial changes as a function of pressure across the structural phase transition showing distinct atomic correlations. The results suggest that the phase transition in in IrTe2 should be an order-disorder like transition of Ir-Ir dimers assisted by Ir-Te bond correlations. X-ray absorption also reveal clear changes in the unoccupied 5d-electronic states and the local geometry with Pt substitution. There is an anomalous spectral weight transfer across the structural phase transition from trigonal to monoclinic, characterizing the reduced atomic structure symmetry. In addition, a gradual increase of the spectral weight transfer is observed in IrTe2, indicating that the low temperature phase is likely to have lower symmetry than the monoclinic. The results suggest that the interplay between inter-layer and intra-layer atomic correlations should have a significant role in the properties of Ir1-xPtxTe2 system.

Authors : Yang Ding,1,* Cheng-Chien Chen,1 Heung-Sik Kim,2 Myung Joon Han,2 Zhenxing Feng,3 Mary Upton,1 Jungho Kim,1 Diego Casa,1 Ayman Said,1 Yufeng Peng,4 Gang Cao,5 Thomas Gog,1 Ho-kwang Mao,4, 6, 7 and Michel van Veenendaal1, 8
Affiliations : 1 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA 2 Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea 3 Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois 60439, USA 4 HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA 5 Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA 6 Geophysical Laboratory, Carnegie Institution of Washington, Washington, D. C. 20015, USA 7 Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, China 8 Department of Physics, Northern Illinois University, De Kalb, Illinois 60115, USA

Resume : Revealing the elementary excitation in the electron strongly correlated systems is the most fundamental means to understand the underlying quantum physics of their novel emergent phenomena, i.e. High T superconductivity. Currently, excitation measurements are typically carried out by angle-resolved photon electron emission spectroscopy (ARPES), scanning tunneling electron microscopy (STEM), or inelastic neutron scattering. However, none of these methods are really compatible with high-pressure conditions, which basically leaves the electron dynamics of the correlated materials at high pressure become a new field in the condensed matter physics to be explored. Hard x-ray resonant inelastic scattering (RIXS) is a new synchrotron method to study the elementary excitations in the electron-correlated-systems, which, mots importantly, is compromised with high-pressure samples environments. Here, we report the first high-pressure RIXS measurements on a high-pressure synthesized singe-crystal Sr3Ir2O7, a newly discovered spin-orbit coupling (SOC) assisted Mott insulator up to 40 GPa through a successful integration of a diamond anvil cell and a resonant inelastic X-ray scattering (RIXS) spectrometer. Our results revealed an interesting evolution of elementary excitation within Ir-5d valence band, such as spin-orbiton excitation, crystal field excitation, magnon excitation, with high-pressure. Moreover, we discovered a new type of excitation that only occurs above 20 GPa in this material. Our results not only demonstrated a first example to directly probe elementary excitation in the d valence band using x-ray at high-pressure, which also promises to a new way to study the electronic structures of electron correlated systems, including cuprates, at high pressure

Authors : T.R. Arslanov
Affiliations : Amirkhanov Institute of Physics, Daghestan Scientific Center, RAS, 367003 Makhachkala, Russia

Resume : Metallic (half-metallic) magnetic clusters embedded in non-magnet semiconductoring matrix provide a potential route toward spin-based devices. The basic advantage of such “hybrid” systems lies in significant remanent magnetization under ambient conditions that is not reached for the classical diluted ferromagnetic semiconductors. However, the control of magnetic characteristics in materials where native phase separations inevitable is still challenging. Here I will review a case of Mn-doped II-IV-V2 semiconductors with general chalcopyrite structure. The experimental and computational results obtained on two central compounds CdGeP2:Mn and ZnGeAs2:Mn will be reported. In contrast to traditional approaches for probing of magnetic semiconductors, I and my co-workers used a high-pressure as tool allowing us to reveal unconventional phase transitions, which caused by phase separated MnP clusters in CdGeP2:Mn. The second part of presentation will be focused on anomalous nature of isothermal magnetization hysteresis and novel pressure-structure-driven magnetoresistance in ZnGeAs2:Mn. Finally, I will show that structural transition in Mn-doped chalcopyrite lattice connected with pressure-induced metallization give rise to qualitative changes in band structure. The accumulated results support the fact that the pressure provides a convenient way to configure the response of cluster systems. This work supported by the RAS Presidium Program P34 “Matter at high pressures”

Authors : Roman Martoňák a, Liliana Grajcarová a b, Michaela Rifliková a, Oto Kohulák a, Erio Tosatti b c
Affiliations : a Department of Experimental Physics, Comenius University in Bratislava, Mlynská dolina F2, 842 48 Bratislava, Slovakia; b International School for Advanced Studies (SISSA) and CNR-IOM Democritos, Via Bonomea 265, I-34136 Trieste, Italy; c The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151 Trieste, Italy

Resume : We study structural and electronic transitions in layered semiconducting materials MoX2 (X = S, Se, Te) upon increasing pressure, employing ab initio DFT based metadynamics and evolutionary search. In MoS2 we found at 20 GPa a layer sliding structural transition converting the 2Hc stacking into the 2Ha one.[1] This explains earlier X-ray and Raman data and has been recently experimentally confirmed.[2,3] In the same pressure region MoS2 undergoes a semiconductor-semimetal transition [1] as also verified by recent experiments.[3,4] The 2Ha structure remains stable until 130-140 GPa where we predict two competing transformation scenarios - chemical decomposition into MoS + S or transformation into a new metastable metallic structure (P4/mmm) with superconducting Tc=16 K.[5] We discuss the relation of our predictions to the recent experiments.[3,4] In MoSe2 and MoTe2 we instead predict metallization at 28 GPa and 13 GPa but no layer sliding transition.[6] The prediction for MoSe2 was also experimentally verified recently.[7] References: [1] L. Hromadová, R. Martoňák, and E. Tosatti, Phys. Rev. B 87, 144105 (2013) [2] N. Bandaru et al., J. Phys. Chem. C 118, 3230 (2014) [3] Z.-H. Chi et al., Phys. Rev. Lett. 113, 036802 (2014) [4] Z. Chi et al., arXiv:1503.05331 [5] O. Kohulák, R. Martoňák, and E. Tosatti, Phys. Rev. B 91, 144113 (2015) [6] M. Rifliková, R. Martoňák, and E. Tosatti, Phys. Rev. B 90, 035108 (2014) [7] Z. Zhao et al., arXiv:1504.08077, Nat. Comm. in press

Authors : Dominik Kurzydlowski, Patryk Zaleski-Ejgierd, Wojciech Grochala, Roald Hoffmann
Affiliations : Faculty of Mathematics and Natural Sciences, Cardinal Stefan Wyszynski University and Centre of New Technologies, University of Warsaw; Institute of Physical Chemistry, Polish Academy of Sciences; Centre of New Technologies, University of Warsaw; Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University

Resume : Noble gases (He–Rn) were long considered as unable to form chemical bonds in neutral molecules, a prejudice refuted by the synthesis of ‘XePtF6’ by Neil Bartlett in 1962 [1]. After nearly half a century of superb (and difficult) experimental work, the chemistry of the heavier ‘noble gases’ (Ar – Rn) is well developed [2]. Yet the high-pressure (p > 1 GPa) chemical and physical properties of noble gas compounds are very poorly understood. To our knowledge there is only one experimental study on the high-pressure polymorphism of a genuine (i.e. not van der Waals complex) noble gas compound, XeF2 [3]. It has been claimed that this difluoride undergoes polymerization at 50 GPa, although our theoretical investigations indicate that XeF2 remains molecular up to 100 GPa [4], but undergoes auto-ionization to [XeF]+F– at a higher compression of 200 GPa. Our recent investigation indicate also that other novel noble gas compounds can be synthesized at relatively small pressures (p < 80 GPa). References: 1. Bartlett, N. Proc. Chem. Soc. 1962, 218. 2. W. Grochala, Chem. Soc. Rev. 2007, 36, 1696. 3. M. Kim, M. Debessai, and C.-S. Yoo, Nat. Chem., 2010, 2, 784. 4. D. Kurzydłowski, P. Zaleski-Ejgierd, W. Grochala, and R. Hoffmann, Inorg. Chem., 2011, 50, 3832.

Authors : Ali ZAOUI
Affiliations : LGCgE, Polytech'Lille, University of Lille 1 Sciences and Technologies

Resume : In this talk I will present some recent results related to surface morphology of carbonates, as well as their behaviors under water and pressure effects. The hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. I will present a detailed recent results concerning structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. In particular, I will show the mechanical characteristics of dry forms of calcium carbonate and hydrous phases. In addition I will talk about the stability of (001) and surfaces of monohydro-calcite, and the (001) surface of ikaite. At the end I will show and discuss the computed morphology pictures obtained from MD simulation and compared to observed SEM images. In addition further recent studies will be shown regarding the interface between clay and carbonate surfaces under anisotropic constrains as well as shear stress. Various mechanical properties will be presented with and without the presence of the water at the interface.

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Authors : Yuichi Shimakawa
Affiliations : Institute for Chemical Research, Kyoto University and Japan Science and Technology Agency, CREST

Resume : Cation ordering in transition-metal oxides often drastically modifies their physical and chemical properties. We here focus on some ordered perovskite-structure oxides, in which transition-metal ions are included at the A and B sites in perovskite ABO3 in ordered manners like AA’3B4O12 and AA’3B2B’2O12. In such compounds A-A, A-B, and B-B interactions compete and/or cooperate with each other and play important roles in giving rise to wide variety of functional properties. Note that many of this structure type compounds are stabilized under high pressure conditions. Recently, we succeeded in obtaining lots of new AA’3B4O12 and AA’3B2B’2O12 oxides by high-presure synthesis. Some of the compounds show intriguing properties. CaCu3Fe4O12 and LaCu3Fe4O12 contain unusually high valence states of iron, and instabilities of the high oxidation states at low temperatures are relieved by charge disproportionation in CaCu3Fe4O12 and by intersite charge transfer in LaCu3Fe4O12. The transitions give significant changes in the properties, and the intersite charge transfer in LaCu3Fe4O12 accomanies a large negative thermal expansion like behavior. The newly discovered A-and-B-site-ordered quadruple perovskite CaCu3Fe2Re2O12 shows ferrimagnetism with an unusually high magnetic transition temperature and large magnetization. More importantly, the electronic structure of CaCu3Fe2Re2O12 is half metallic, and the compound shows large magnetoresistance by conduction of spin-polarized electrons.


Symposium organizers
Wei LUOUppsala University | Department of Physics & Astronomy

Box 516 75120, Uppsala Sweden

+46 18 4713511
Maurizio MATTESINIUniversidad Complutense de Madrid - Departamento de Física de la Tierra, Astronomía y Astrofísica I (Geofísica y Meteorología)

Madrid Spain

+34- 91 394 5164
Hongting SHIBeijing Institute of Technology (USTB)

No. 5 Zhongguancun South Str. 100081 Bejing, China