<div dir="ltr"><div dir="ltr">Hi Leo<div><br></div><div>Thanks for the help. I started a CASTEP calculation on the CP2K twisted (relaxed) geometry and it converged as twisted, and this CASTEP relaxed twisted geometry is more stable than the untwisted version by a factor of 0.00030737 eV. Gamma point was used for both twisted and untwisted
calculations.</div><div><br></div><div>Moreover, I have tried the CP2K calculation as you suggested to untwist the geometry but it converged as twisted. I am using CP2K 7.1 and the only change that I have made in the input was the removal of the following lines: </div><div><br></div><div> #COORD_FILE CP2K_Optimzed structure_CIF.cif<br> #COORD_FILE_FORMAT CIF<br></div><div><br></div><div>Are there any significant changes between 7.1 and 8.1 in terms of dealing with symmetry...?</div><div><br></div><div>-Monu</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Feb 24, 2021 at 3:50 AM Leopold Talirz <<a href="mailto:leopol...@gmail.com">leopol...@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">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 <a href="http://925-pos-1.xyz" target="_blank">925-pos-1.xyz</a>" 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:0px 0px 0px 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 rel="nofollow">leo...@gmail.com</a>> wrote:
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