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Distinction between space groups having principal rotation and screw axes, which are combined with twofold rotation
K Saitoh1, K Tsuda, M Terauchi
1Research Institute for Scientific Measurements, Tohoku University, Sendai 980-8577, Japan. saitohk@yamame.rism.tohoku.ac.jp
Abstract:
23 sets of space groups remain indistinguishable by the convergent-beam electron diffraction (CBED) method. Recently, Tsuda, Saitoh, Terauchi, Tanaka & Goodman [Acta Cryst. (2000), A56, 359-369] demonstrated that the coherent CBED method can distinguish two space-group pairs (I23, I2(1)3) and (I222, I2(1)2(1)2(1)) by observing the relative arrangements of 2-fold-rotation and 2(1)-screw axes. The other ten space-group sets, which are composed of principal rotation and screw axes and other 2-fold-rotation axes such as P321 and P3(1)21 (P3(2)21), are shown to be distinguishable using the coherent CBED method.