Prof. Juri Grin [Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany]

Title: Atomic interactions in intermetallic compounds and their chemical and physical properties

Time: 10:00 - 11:00 AM, Wednesday, May 25, 2016

Place: Auditorium Room 410, HPSTAR (Shanghai)

Host: Dr. Ho-Kwang Mao

Abstract:

Intermetallic compounds reveal chemical and physical behaviors interesting for applications and may serve as basic components for materials design. In particular chemical catalysis, thermoelectric or heavy-fermion behaviors are in focus recently. An attempt to find a direct link between the properties and the crystal structure as well the atomic interactions for this group of inorganic substances revels often a lack of reliable information on all three, crystal structure, bonding and properties, hindering studies on their relationship.

In particular chemical bonding in intermetallic compounds is a rather open question. An application of modern quantum-chemical tools like Electron Localizability approach (ELI-D) opens access to the bond definition in real space [1], allows revealing of the – on first glance unexpected - relation between organometallic and intermetallic compounds of rare–earth metals [2] or opening the way to unique definition of the important categories of chemical bond descriptors like covalence or ionicity [3] or polarity [4]. This gives a possibility of Zintl-like interpretation for large group of intermetallic phases [4,5] and yields a connection to the basic information about possible band structure [6].  

The ELI-D approach allows differentiation of covalent, ionic and lone-pair contributions to the atomic interactions [4]. So, the formation of the lone pairs around the defects in the Ge framework in the clathrate Ba8Ge43□3 and the covalent Ba-Au interactions in the clathrate Ba8AuxGe46-x-y□y as well polar interactions Cu-Se and Cu-Sn in Cu2SnSe3 [7] were detected. Both findings yield to the special features of the electronic DOS, which were confirmed by measurements of electronic and thermal transport. Bonding-caused features in the boride TmAlB4 result in new magnetic interactions [8]. Understanding of the chemical bonding in intermetallic compounds opens a way to novel redox-based preparation routes. So the binary clathrates Ba8Si46 [9] and Na24Si136 [10] – were prepared and their transport properties were investigated. Another bonding-based concept dealing with the intermetallic phases is the isolated-site model for catalysis. New catalysts for semi hydrogenation of acetylene based on the well-crystallized intermetallic compounds GaPd and Al4Fe13 were suggested employing the ideas of the covalent atomic interactions in intermetallic compounds [11,12].

 [1] F. R. Wagner et al. Chem. Eur. J. 108 (2007) 5724.

 [2] M. V. Butovski et al. Nature Chem. 2 (2010) 741.

 [3] D. Bende at al. Chem. Eur. J. 20 (2014) 9702.

 [4] D. Bende et al. Inorg. Chem. 54 (2015) 3970.

 [5] D. Bende, Yu. Grin, F. R. Wagner, In: Heusler Alloys, Springer, 2016, 133ff.

 [6] Yu. Grin. In: Comprehensive Inorganic Chemistry II, vol 2. Oxford: Elsevier; 2013, 359ff.

 [7] J. Fan et al. Inorg. Chem. 52 (2013) 11067.

 [8] T. Mori et al. J. Appl. Phys. 107 (2010) 09E112.

 [9] J. Liang et al. Inorg. Chem. 50 (2011) 4523.

 [10] M. Beekman et al. Phys. Rev. Lett. 104 (2010) 018301.

 [11] M. Armbrüster et al. J. Am. Chem. Soc. 132 (2010) 14145.

 [12] M. Armbrüster et al. Nature Materials, 11 (2012) 690.

Biography of the Speaker:

Prof. Juri Grin was born on July 23, 1955 in Lviv (Lemberg, Ukraine). Study of chemistry and doctorate Lemberg University, Director and Scientific Member at the Max Planck Institute for Chemical Physics of Solids (since 2001).

The Max Planck Institute for Chemical Physics of Solids is dedicated to the discovery of new materials with unusual properties. To this end, researchers must have a fundamental understanding of the interrelations between the atomic structure, chemical bonding, electron states and the properties of a compound. The key research focus of the Institute is compounds of different metals. Chemists and physicists as well as experimental and theoretical scientists use state-of-the-art instruments and methods to investigate how the chemical composition, configuration of atoms and external forces affect the behaviour of electrons. It is these that are responsible for the magnetic, electronic and chemical properties of the compounds, and thus for their potential use as materials.