J. Phys. IV France 112 (2003) 727
DOI: 10.1051/jp4:2003985

Crystal structure of orthorhombic martensite in TiNi-Cu and TiNi-Pd intermetallics

P.L. Potapov¹, S.E. Kulkoval², A.V. Shelyakov³, K. Okutsu⁴, S. Miyazaki⁴ and D. Schryvers<sup>1

1</sup>  EMAT, University of Antwerp, RUCA, Groenenborgerlaan 171, 2020 Antwerp, Belgium
²  Institute of Strength Physics and Material Science, Akademichesky 2/1, 634021 Tomsk, Russia
³  Moscow Engineering Physics Institute, Kashirskoe Sh. 31, Moscow, Russia
⁴  Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan

Abstract
The crystal structure of orthorhombic martensite in ternary TiNi-based compounds has been several times examined, although, in all cases, the structure was not completely solved as the positions of atoms in the unit cell remained unknown. In the present work, the X-ray patterns of TiNi-Cu and TiNi-Pd films were refined by the Rietveld method revealing important regularities in the location of Ti and Ni atoms. In particular, the (010) atomic planes in the orthorhombic martensite structure are always distorted and loose the planar centre of symmetry. This observation was confirmed by ab-initio calculations, where the atomic positions were varied in order to minimise the energy of electron bands.

© EDP Sciences 2003