[CP2K-user] [CP2K:18265] Difference between CP2K and Gaussian on 4th period transition metals

Elvis elvisnwh at gmail.com
Wed Dec 28 16:13:58 UTC 2022


I am seeing very dramatic difference between TDDFT spectra obtained by 
Gaussian and CP2K. I am not sure if I should just trust the built in basis 
set / pseudopotential.

First of all, for some systems, e.g. H2O, pyridine or pyZnCO3, the spectra 
are very similar,  when using large cell or with wavelet solver, and using 
large enough cutoff. One example is shown below. Even though CP2K and 
Gaussian uses very different pseudopotentials and also very different 
algorithms in implementations, we can see qualitative match between the two 

(e.g. pyZnCO3)
[image: Zn.png]

However, when the Zn is replaced by Cd, or other 4th period transition 
metals. The spectra are no longer similar. One example is shown below.

(e.g. pyCdCO3, where the spectra are very different. )

[image: pyCdCO3.png]

I have tried different cutoff values, different cell sizes, non-periodic 
wavelet solver, no or larger cutoff for truncated 1/r potential for HFX, 
finer grid etc. and none of them resulted in better match between the two 
softwares. It should be pointed out that the good match for H2O, py or even 
pyZnCO3 (where the only difference is Zn replacing Cd) showed that the 
software was set up correctly and the mismatch should not be due to wrong 
software setting. This mismatch also happens for test molecule, CdO and 
PdO, and therefore not an isolated example.

I can understand that this difference is due to the different 
pseudopotential used with CP2K and Gaussian. However, in Gaussian, even 
different ECPs (Lanl2dz or SDD) gave qualitatively similar results. 

I am a bit concerned about the big difference between the two softwares 
when Cd or other 4th period transition metal (e.g. Pd) is involved. Can 
anyone comment on this? Any suggestion or comment for me will be greatly 
appreciated. *I am not sure if I should just trust the built in basis set / 
pseudopotential and just proceed with my complex system.*

Thanks again.

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