Spontaneous distortions of the crystal symmetry

What is not shown in the tables, are spontaneous distortions of the crystal symmetry, which are usually very small (i.e. < 10-4) and have only been observed in cubic systems, where the detection of symmetry distortions is easier. To our knowledge the largest symmetry breaking effect has been observed for cubic GdZn by Rouchy et al. (1981), namely a tetragonal distortion of (A///)ooi -3.7 x 10-4 (see section 5). 

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