Hi Monu,<div><br></div><div>thanks for following up - I did run a CP2K cell optimization starting from your relaxed "twisted" CP2K geometry. You find the trajectory and movie attached</div><div>Does this agree with your results?</div><div><br></div><div>It certainly seems to "untwist" the ligands (see movie) - I had to stop the optimization at some point though because convergence became very slow.</div><div><br></div><div>Some stats from the total energy:<br></div><div><br></div><div>First total energy (single-point): -2160.041714658635101</div><div>First optimization step: -2160.136731180092738</div><div>50th optimization step: -2160.2817551900</div><div>100th optimization step: -2160.2996248085</div><div><br></div><div>I.e. after the first "untwisting" that lowers total energy by ~260mHa (quite significant), the final 50 steps lower the total energy by less than 3 mHa.</div><div>This is with cp2k 8.1 [2] and with minimal modifications to the input file (see tar file). It's not clear to me why you would get a different result - both MULTIPLE_UNIT_CELL 1 1 2 and 2 2 2 K-points should give this result.</div><div><br></div><div>As to why the CASTEP gamma point calculation does not yield the twisted structure: it is possible that this involves breaking a symmetry that is for some reason preserved in the CASTEP calculation (don't know).</div><div>Can you try starting your CASTEP calculation from the twisted CP2K geometry and see where it ends up?</div><div>If it remains twisted, you can then compare total energies to the untwisted result, which should tell you which one is the actual minimum.</div><div><br></div><div>Best,</div><div>Leo</div><div><br></div><div>[1] Try "grep i 925-pos-1.xyz" on the trajectory</div><div>[2] Our previous calculations were with cp2k v5.1 though.</div><div><br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Tuesday, 23 February 2021 at 05:45:09 UTC+1 Monu Joy wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div><div style="font-family:verdana,helvetica,sans-serif;font-size:13px"><div><div dir="ltr"><div><div dir="ltr" style="font-family:verdana,helvetica,sans-serif">Even though the doubling of the z-axis (MULTIPLE_UNIT_CELL 1 1 2) seemed fine in the initial cycles, it ended up being twisted on convergence. Then I have tried the K-point scheme (SCHEME MONKHORST-PACK 2 2 2), where the result was the same, twisted. However, the structure seems reasonable (no twisting) in CASTEP even with the gamma point.</div><div dir="ltr" style="font-family:verdana,helvetica,sans-serif"><br clear="none"></div><div dir="ltr" style="font-family:verdana,helvetica,sans-serif">But of course, the culprit could be the small z-axis, but I am not sure how to tackle this in CP2K.</div><div style="font-family:verdana,helvetica,sans-serif"><br clear="none"></div><div style="font-family:verdana,helvetica,sans-serif"><div dir="ltr" style="font-size:small">-Monu</div></div></div></div></div>
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On Friday, 19 February, 2021, 05:25:24 pm GMT-5, Leopold Talirz <<a href data-email-masked rel="nofollow">leo...@gmail.com</a>> wrote:
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