<div dir="ltr">Hello, I have recently carried out a cell optimization of a (3,2,1) supercell of croconic acid (see croc_uc.xyz) with CP2K v6.1. I have attached the input file as crca_20181229_112044_000.inp and linked the output files (in 2 parts) <a href="https://drive.google.com/file/d/1x7jmZEkIpeROmqoBn-2B8t6N6XLoCgxv/view?usp=sharing">crca_20181229_112044_000.out</a> and <a href="https://drive.google.com/file/d/1x7jmZEkIpeROmqoBn-2B8t6N6XLoCgxv/view?usp=sharing">crca_20181229_112044_000_restarted.out</a>. I am having problems with the values that CP2K returned for the relaxed cell dimensions, however. These were [25.474, 10.328, 10.866]. I thought that this implied unit cell dimensions of [8.491, 5.164, 10.866]; however, the displacement between corresponding atoms in unit cells that are alongside each other in the x-direction within the supercell is [8.721, 0.0, 0.0]. Similarly, the displacement between corresponding atoms in unit cells that are alongside each other in the y-direction is [0.0, 5.274, 0.0]. These do not appear to be consistent with the relaxed cell dimensions produced by the CP2K cell optimization. To investigate further, I generated two (6,2,1) supercells made by joining two (3,2,1) supercells in the x-direction. (6,2,1) supercell A has the second (3,2,1) supercell displaced by [25.474, 0.0, 0.0] from the first (i.e. the a-dimension given by CP2K's cell optimization), while (6,2,1) supercell B has the second (3,2,1) supercell displaced by [26.163, 0.0, 0.0] = 3*[8.721, 0.0, 0.0] from the first. For supercell A, at the boundary between the (3,2,1) supercells, the O-H bonds are vertical, instead of diagonal to be consistent with the crystal structure. For supercell B, at O-H bonds at the boundary are diagonal and consistent. I've attached the xyz files and VESTA screenshots of the 2 supercells. Could somebody, please, explain why the supercell dimensions given in the cell optimization output are not consistent with the true cell dimensions? Or am I misinterpreting these values? I have done cell optimizations with both the TZV2P-MOLOPT-GTH and DZVP-GTH-PBE basis sets and have only experienced this problem with TZV2P-MOLOPT-GTH. Best wishes, Matthew </div>