[CP2K-user] [CP2K:21049] Differences Between Mulliken and Hirshfeld Charge Analysis

[Thomas Kühne]

Dear Kha Trinh, 

the results of population analyses such as Mulliken population analysis and charge analyses such as Hirscheld and DDEC charges are 
not unique and may severely differ - in some cases even within the sign! As such the differences you observe are within what to expect. 

Best regards, 
Thomas Kühne

> Am 14.01.2025 um 02:21 schrieb Kha Trinh <minhkha010301 at gmail.com>:
> 
> 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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