Announcements

KABAM-CHEMISTRY JOINT SEMINAR by Yuri Grin

Author: COLLEGE OF SCIENCES
Time: 14:30
Location: CASE 216

KOÇ UNIVERSITY KABAM-CHEMISTRY JOINT SEMINAR
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Speaker        : Yuri Grin, Max-Planck-Institut für Chemische Physik fester Stoffe

Title              : Chemical bonding and properties of intermetallic compounds

Date              : Tuesday, November 12, 2019
Time             :
 14:30
Cookie&Tea: CASE 216, 14:15
Place             : CASE 216

 

Abstract:  
 

Intermetallic compounds are formed by elements located left from the Zintl line in the Periodic Table.

They 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 at the Department of Chemical Metals Science of the Max-Planck-Institut

für Chemische Physik fester Stoffe in Dresden. 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. For interpretation of their chemical and physical properties a better

understanding of the composition and bonding in crystal structures of these substances is necessary.

Especially the chemical bonding in intermetallic compounds is a rather open question [1]. An application

of new quantum-chemical tools in real space like electron localizability approach [2-4] opens the way

to real-space definition of the basic categories for chemical bonding description like covalence or

ionicity [5] or polarity [6].

So, the formation of the covalent Ba-TM interactions in the clathrates Ba8TMxGe46-x-y□y [7] as well polar

interactions Cu-Se and Cu-Sn in Cu2SnSe3 [8] 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 [9].

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 [10,11]. Recently, the chemical behaviour of CaAg2 and CaAg under

ethylene epoxidation was studied. Unexpectedly, the CaAg (010) surface possesses an outstanding

stability during long-term experiments. This is caused by the anisotropy of chemical bonding and the

formation of a highly ordered, stable and dense CaO layer with a small amount of embedded Ag atoms

which prevents further oxidative decomposition [12-14].

1. Yu. Grin. In: Comprehensive Inorganic Chemistry II, Vol 2, Oxford Elsevier, 2013, p. 359.

2. M. Kohout, Faraday Discuss. 2007, 135, 43.

3. F. R. Wagner et al. Chem. Eur. J. 2007, 13, 5724.

4. A. Martin-Pendas et al. In: Modern Charge-Density Analysis, Springer, 2012, p. 303.

5. D. Bende at al. Chem. Eur. J. 2014, 20, 9702.

6. D. Bende et al. Inorg. Chem. 2015, 54, 3970.

7. A. Ormeci, Yu Grin. J. Thermoelectricity, 2015, № 6, 16.

8. J. Fan et al. Inorg. Chem. 2013, 52, 11067.

9. T. Mori et al. J. Appl. Phys. 2010, 107, 09E112.

10. S. A. Villaseca et al. ChemPhysChem. 2017, 18, 334.

11. M. Armbrüster et al. Nature Mater. 2012, 11, 690.

12. I. Antonyshyn et al. Eur. J. Inorg. Chem. 2018, 35, 3933.

13. I. Antonyshyn et al. Inorg. Chem. 2018, 57, 10821.

14. I. Antonyshyn et al. Sci. Technol. Adv. Mater. 2019, 20, 903.