A short note about diffuse Bieberbach groups

We consider low dimensional diffuse Bieberbach groups. In particular we classify diffuse Bieberbach groups up to dimension 6. We also answer a question from [S. Kionke, J. Raimbault, On geometric aspects of diffuse groups, Doc. Math. 21 (2016), page 887] about minimal dimension of a non-diffuse Bieberbach group which does not contain three-dimensional Hantzsche-Wendt group.