Complex intermetallic compounds and metal hydrides from powder diffraction

 

Radovan Černý

 

Laboratory of Crystallography, University of Geneva

Radovan.Cerny@cryst.unige.ch

 

Intermetallic compounds are playing important role in many technological applications (high performance construction materials, magnetic materials, hydrogen storage). The characterization of their crystal structure is not an easy task due to often presence of lattice defects, chemical disorder, pseudosymmetry and weak superstructures. The fact that the intermetallic structures do not contain easily recognizable building units like molecules, and that they are often build up from atoms with large scattering contract, does not simplify their structural characterization by diffraction methods either. The single crystals are often not available, and structure size can reach few hundreds of independent atoms.

In the talk we will review the pitfalls of the structural characterization of intermetallic compounds by X-ray and neutron powder diffraction. Different tools of structure characterization of intermetallic compounds and their hydrides like high reciprocal space resolution [1], resonant diffraction [2], in-situ studies [3], methods and programs for structure solution [4] will be discussed with examples from our work.

 

  1. Černý R., Renaudin G., Favre-Nicolin V., Hlukhyy V. and Pöttgen R.: Mg1+xIr1–x (x = 0, 0.037 and 0.054), a Binary Intermetallic Compound with a New Orthorhombic Structure Type from Powder and Single Crystal X-ray Diffraction. Acta Cryst. B60(2004)272-281

 

  1. Joubert J.-M., Černý R., Latroche, M., Percheron-Guégan, A. and Yvon K: Site Occupancies in the Battery Electrode Material LaNi3.55Mn0.4Al0.3Co0.75 as Determined by Multiwavelength Synchrotron Powder Diffraction. J. Appl. Cryst. 31(1998)327-332

 

  1. Joubert J.-M., Černý R., Latroche M., Percheron-Guégan A. and Schmitt B.: Hydrogenation of LaNi5 studied by in situ synchrotron powder diffraction. Acta Materialia 54 (2006) 713–719

 

  1. Favre-Nicolin V. and Černý R.: A better FOX: using flexible modeling and maximum likelihood to improve direct-space ab initio structure determination from powder diffraction. Z. Krist. 219(2004)847-856.