[CP2K-user] [CP2K:21803] Mismatch between CP2K computed Force constant (a.u)and Gaussian computed force constant(mDyne/angstrom)

[Johann Pototschnig]

You are still missing the "PERIODIC NONE" in the SUBSYS section:
https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/SUBSYS/CELL.html#CP2K_INPUT.FORCE_EVAL.SUBSYS.CELL.PERIODIC

There is a warning in your output.

On Friday, September 5, 2025 at 8:42:47 PM UTC+2 Naina Sethi wrote:

> Dear Prof. Hutter,
> Is there any mistake in my input setup? Could you please help.
>
> On Monday, August 25, 2025 at 3:05:15 PM UTC+5:30 Naina Sethi wrote:
>
>> I am using CP2K version 2024.3 and attempted to reproduce one of the 
>> sample calculations on the benzene molecule (
>> https://www.cp2k.org/exercises:2015_ethz_mmm:infra_red). However, I am 
>> unable to obtain force constants similar to those that i get from gaussian. 
>> While the vibrational frequencies, IR intensities, and reduced masses agree 
>> perfectly with Gaussian results, the force constants differ 
>> significantly(specifically for lower frequency regime). This discrepancy is 
>> concerning because the magnitude of the force constants is critical for my 
>> work. Could you please advise whether this might be related to changes in 
>> the code since the example was prepared, or if I might be missing something 
>> in my setup?
>>
>> I am attaching the Input and output files from CP2K and gaussian 
>> calculation. Kindly suggest. 
>>
>> Thank you very much for your time and guidance.
>>
>> Best regards,
>>
>>

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