Professor Lee Cronin, University of Glasgow, UK
Materials discovery - from atomic energy landscapes to phase diagrams
Professor Martin Jansen, Max Planck Institute for Solid State Research, Germany
Superconductivity and the Periodic Table: From elements to materials
Professor Arndt Simon, Max Planck Institute for Solid State Research, Germany
Superconductivity represents a coherent state of paired conduction electrons. Attraction of particles with the same charge seems puzzling, however, chemists are all too familiar with paired electrons, though localised in covalent bonds. We follow the idea that under certain conditions conduction electrons exhibit a tendency towards pairwise localisation through dynamic covalency. Based on a special feature in the normal state electronic band structure, the necessary condition for a metal to become a superconductor is the simultaneous occurrence of flat and steep bands at the Fermi level. This feature occurs with no exception for metals which finally become superconducting at low temperature. However, the sufficient condition at least for conventional superconductors is a strong enough coupling of flat band states to lattice vibrations, phonons. The idea of such a flat band/steep band scenario is tested with actual examples, starting from an element, Te, via the rare earths compounds RE2X2C2, REC2, RE2C2 to MgB2. The latter is particularly suited to illustrate the aspect of dynamic covalency. As a surprise, a peak-like structure of the electron-phonon coupling constant in momentum space with an enormous enhancement for non-commensurate phonon vectors is found. It is interesting to follow the historical evolution of thoughts concerning the phenomenon of superconductivity. Steps of a staircase are marked by Planck, Bose, Einstein, London, and finally Ogg, who discovered the essential role of electron pairs for superconductivity. His sensational report of superconductivity at 190K in quenched solutions of Na in NH3, however, could not be reproduced. It is tempting to perform experiments along the lines of this visionary scientist under more stringent conditions. Preliminary results from an emeritus with administrational freedom are reported.
Professor Anthony Cheetham FRS, University of Cambridge, UK
Chemistry of Ag(2+): a cornucopia of pecularities
Professor Wojciech Grochala, CENT, University of Warsaw, Poland
Silver is the heavier congener of copper in the Periodic Table, but chemistry of these two elements is very different. While Cu(II) is the most common cationic form of copper, Ag(II) is rare  and its compounds exhibit a broad range of peculiar physicochemical properties. These include, but are not limited to:
- uncommon oxidizing properties
- unprecedented large mixing of metal and ligand valence orbitals
- strong spin-polarization of neighbouring ligands (L), which leads to:
- record large magnetic superexchange constants and also
- ease of thermal decomposition of its salts as well as
- robust Jahn–Teller effect which is preserved even at high pressure.
The powerful oxidizing properties of Ag(II) are revealed not only in its behaviour towards inorganic and organic reagents, but also in its capability to oxidize oxo- and even fluoro- ligands from its first coordination sphere. Notably, all oxo-derivatives of Ag(II) are metastable and they decompose exothermally at temperatures not exceeding 120 oC [2,3,4]. Moreover, the formal redox potential of Ag(II) in 30% oleum approaches +2.9 V vs. NHE, the largest value ever measured for a fluorine-free system . The electrochemically generated Ag(II) species are short-lived since they are capable of oxidizing the superacidic solvent . Having in mind that the standard redox potential for the ½ Cl2 / Cl– redox pair is as small as + 1.36 V vs. NHE, it is no surprise that Ag(II)Cl2 has never been prepared.
The strong Ag(4d)/L(2p) mixing (where L = F, O, N etc.) is revealed in the XPS spectra [6,7] and confirmed by quantum mechanical calculations. Since Ag(II) is a spin-½ cation, it also transfers spin density to the ligands. Appreciable share of free spin in both metal and ligand valence orbitals results in very large magnetic superexchange constants which may exceed 100 meV , with the possibility of the record value of up to 300 meV for a 1D system . The quest continues for a 2D system with equally strong antiferromagnetic interaction, which could serve as a precursor towards a room-temperature supeerconductor. As all d9 systems, compounds of Ag(II) are susceptible towards Jahn–Teller effect. The JT effect is strong as it usually leads to appreciable elongation (or, rarely, shortening) of the AgL6 octahedron. It also proves to be quite robust as it is preserved at high pressure of up to 30 GPa for Ag(II)SO4 .
 W. Grochala, R. Hoffmann, Angew. Chem. Int. Ed. Engl. 40 (2001) 2742.
 P. Malinowski et al., Angew. Chem. Int. Ed. Engl. 49 (2010) 1683.
 P. Malinowski et al., Chem. Eur. J 17 (2011) 10524.
 P. Malinowski et al., CrystEngComm 13 (2011) 6871.
 P. Połczyński et al., Chem. Commun. 49 (2013) 7480.
 W. Grochala, et al., ChemPhysChem 4 (2003) 997.
 A. Grzelak et al., submitted (2014).
 D. Kurzydłowski et al., Chem. Commun. 49 (2013) 6262.
 T. Gilewski et al., in preparation (2014).
 M. Derzsi et al., CrystEngComm 15 (2013) 192.
The chemistry of nanospace
Professor Susumu Kitagawa, Kyoto University, Japan
Materials with nanosized spaces, often known as porous materials, are abundant in everyday modern life: they are used for gas storage, separation, and catalysis. Based on a new concept of bottom-up synthesis, we are now able to successfully develop novel porous materials including everything from serendipitous findings to tailor-made synthesis. These are called "porous coordination polymers" (PCPs) or "metal–organic frameworks" (MOFs), which are comprised of organic and inorganic materials. We have developed the functional chemistry of PCPs, discovered flexible porous materials, and created soft porous crystals, unlike anything available via conventional methods. Today several hundred different PCPs are known, and over 2,000 articles on this class of materials are being published annually worldwide. PCPs have great potential in applications for our immediate surroundings as well as a wide variety of fields, such as the global environment, natural resources, development of outer space, life sciences, and energy, demonstrating their extremely high value both for science and for industry.
A Periodic Table of metal oxides
Dr David Payne, Imperial College London, UK
The 20th century is often known as the age of silicon and the 21st century is predicted to be the age of graphene, while the former has undoubtedly benefited our societies and economies, the latter holds a great promise but is yet to find widespread use. Beyond the elements alone there is of course a wider class of materials used in countless industrial, technological and medical applications – the oxides. This talk will focus on a “Periodic Table of Oxides” whose properties vary from insulating to semiconducting to metallic to superconducting, from transparent to absorbing to reflective and from varying types of magnetism to hosting some of the most exotic states discovered at the frontiers of condensed matter science. To highlight the importance of understanding these materials this talk will focus on oxides such as lead dioxide (lead/acid battery) and indium oxide and ITO (flat screen displays). The need to apply state-of-the-art photoelectron spectroscopies in order to fully understand the electronic structure of these technologically vital materials will be highlighted, work performed in collaboration with theoretician colleagues using density functional theory. To finish we will discuss the next generation of spectroscopic techniques – particularly high-pressure photoelectron spectroscopy (HiPPES) – a technique that promises a step-change in the understanding of oxide surfaces.