Observation of antiphase domain structure in chlorapatite
Journal of Applied Crystallography
Volume 30, Issue 6, pages 1148–1149, December 1997
How to Cite
Yang, X.-M. (1997), Observation of antiphase domain structure in chlorapatite. Jnl Applied Crystallography, 30: 1148–1149. doi: 10.1107/S0021889896012940
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Single-crystal electron-diffraction patterns of synthetic chlorapatite [Ca5(PO4)3Cl] show weak reflections violating the space group P21/b. Transmission electron microscopy with dark-field imaging, using hk0 (k = even) reflections, which are allowed for P21/b, reveals no special features, while dark-field viewing through certain superstructure reflections [hk0 (k = odd), which are forbidden for this space group] reveals antiphase domains. Diffraction-contrast experiments show that these domains are related by a displacement vector R = ½. This displacement vector explains the origin of the domain in terms of the ordering of the Cl-ion position in the channels of chlorapatite.