Distinction of space groups (<i>I</i>23 and<i>I</i>2₁3) and (<i>I</i>222 and<i>I</i>2₁2₁2₁) using coherent convergent-beam electron diffraction

Abstract

Convergent-beam electron diffraction (CBED) is well known as a powerful tool to determine space groups of crystals. However, it cannot distinguish several sets of space groups. It is shown theoretically that the coherent CBED method can distinguish between space groups (I23 and I2(1)3) and between (I222 and I2(1)2(1)2(1)), which belong to indistinguishable sets. It is demonstrated by computer simulations that the relative arrangement of 2-fold-rotation and 2(1)-screw axes can be distinguished by examining the relative phases of specific reflections through the interference fringes of coherent CBED patterns. This fact implies that these space groups can be distinguished by the coherent CBED method.