[CP2K-user] [CP2K:21039] Differences Between Mulliken and Hirshfeld Charge Analysis

[Kha Trinh]

Dear CP2K Users,

I’m working on the geometry optimization of a transition state featuring an 
*O--Li--O* structure using CP2K and ASE. As part of the analysis, I 
calculated Mulliken and Hirshfeld charges, but I noticed significant 
discrepancies between the two methods.

Here are the results for two cases of the transition state:

*Mulliken Charges:*

Oxygen (O): -0.361

Lithium (Li): 0.565

Oxygen (O): -0.367

*Hirshfeld Charges*

Oxygen (O): -0.261

Lithium (Li): -0.470

Oxygen (O): -0.265

The results from Mulliken and Hirshfeld methods show opposite trends 
regarding the charge on the Li atom. The Hirshfeld analysis, in particular, 
seems counterintuitive because I would expect lithium, located between two 
oxygen atoms, to have a partially positive charge. However, in my field, it 
is more common to report Mulliken charges.

Could this discrepancy arise from the charge partitioning methods or my 
calculation settings? My system includes C, H, O, N, and Li atoms, using 
the DZVP-GTH basis set and GTH-PBE functional. Any advice on interpreting 
or validating these results would be greatly appreciated. I have attached 
the relevant input and output files for reference. 

Thank you so much in advance

Best regards,
Kha

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