[CP2K-user] [CP2K:18937] k-points vs. supercell approach

[Léon Luntadila Lufungula]

Dear CP2K community,

I'm quite new to CP2K and I am trying to build my input files step-by-step 
to eventually do calculations on modified surfaces. Currently I'm still 
doing single point calculations on my bulk structure (anatase TiO2) to 
optimize the calculation parameters. I have already converged the values of 
the CUTOFF and REL_CUTOFF parameters and was now looking at comparing 
k-point sampling to gamma point calculations within the supercell approach. 

I was initially thinking about using the supercell approach as some things 
are not yet implemented for k-points, such as the OT method for example, 
but I noticed that supercell calculations are considerably slower than 
k-point calculations. I have attached the input and output files for both 
approaches for the largest cell/k-mesh I have used, which is 5x5x2. The 
k-point calculation only took 14.342s, whereas the supercell calculation 
took a whopping 649.442s...

So my question is if I should just continue with k-points sampling or if 
there is something wrong with my inputs which results in the large 
difference in calculation time? The k-point calculation also throws a 
warning "*** WARNING in cryssym.F:165 :: Symmetry library SPGLIB not 
available ***", but I also don't know if this may be the reason for the 
discrepency or if I may ignore this warning.

Any help would be greatly appreciated!

Kind regards,
Léon

-- 
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/d6ab8642-af3b-4858-9212-cd68a8514aaan%40googlegroups.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230619/b7a8d0ef/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: anatase.cif
Type: chemical/x-cif
Size: 1682 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230619/b7a8d0ef/attachment-0001.cif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: anatase_supercell_5-5-2.out
Type: application/octet-stream
Size: 298613 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230619/b7a8d0ef/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: anatase_kpts_5-5-2.out
Type: application/octet-stream
Size: 86043 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230619/b7a8d0ef/attachment-0003.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: anatase_supercell_5-5-2.inp
Type: application/x-shellscript
Size: 2268 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230619/b7a8d0ef/attachment-0002.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: anatase_kpts_5-5-2.inp
Type: application/x-shellscript
Size: 2319 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230619/b7a8d0ef/attachment-0003.bin>