Acta Crystallographica Section A

Foundations of Crystallography

Volume 59, Part 2 (March 2003)

research papers

Acta Cryst. (2003). A59, 117-126 [ doi:10.1107/S0108767302022559 ]

Structure of Ti₂P solved by three-dimensional electron diffraction data collected with the precession technique and high-resolution electron microscopy

M. Gemmi, X. D. Zou, S. Hovmöller, A. Migliori, M. Vennström and Y. Andersson

Abstract: The crystal structure of Ti₂P has been analysed using electron diffraction and high-resolution electron-microscopy techniques. A new unit cell was found, the compound is hexagonal with a = 19.969 (1) and c = 3.4589 (1) Å. The structure was first solved in space group $P{\bar6}2m$ in projection using direct methods on electron diffraction data from the [001] zone axis. A three-dimensional solution was obtained using again direct methods but on a three-dimensional set of electron diffraction data recorded with the precession technique. Ti₂P is a distorted Fe₂P structure and, based on high-resolution images, it is possible to explain that the tripling of the unit cell is due to the ordering of P vacancies that reduces the symmetry to $P\bar6$ .

Keywords: electron crystallography; electron diffraction; precession technique.