[CP2K-user] [CP2K:22188] Re: ONIOM in CP2K

['daniel Storm' via cp2k]

Hi Marcella,

Thanks for your response. 

I tried including MULTIPLE_SUBSYS T in the MULTIPLE_FORCE_EVALS section and 
unfortunately that gives me the same error as before. 

I have also tried varying the size of my QM region. This system has 4 
cations and 4 cations in it with an overall charge of 0. I’ve tried having 
my QM region as;

-              -   1 cation (Charge 1)

-              -   1 cation + 1 anion (Charge 0)

These unfortunately produce similar errors to above.

Kind regards,
Daniel

On Wednesday, April 15, 2026 at 5:01:14 PM UTC+1 Marcella Iannuzzi wrote:

> Hi 
>
> I think you need to specify 
> MULTIPLE_SUBSYS 
> <https://manual.cp2k.org/trunk/CP2K_INPUT/MULTIPLE_FORCE_EVALS.html#CP2K_INPUT.MULTIPLE_FORCE_EVALS.MULTIPLE_SUBSYS>
>  T
>
> in &MULTIPLE_FORCE_EVALS .. &END
>
>  Kind regards
> Marcella
>
> On Tuesday, April 14, 2026 at 5:27:49 PM UTC+2 dstor... at googlemail.com 
> wrote:
>
>> Hi everyone,
>>
>> To provide some context, I am working with an iridium organometallic 
>> salt, [Ir(PONOP)(H)Me][BArF4] and my goal here is to do a QM/MM type 
>> calculation where my MM region is treated with xTB.
>>
>> I have tried my best to piece together an ONIOM input file from what I’ve 
>> seen on the internet but it’s not quite right. I keep getting a CPASSERT 
>> error suggesting that there is an issue with how the fragments are 
>> numbered? I’ve double-checked those and it looks correct to me.
>>
>> My QM region (Fragment 1) are atoms 406-545
>>
>> My xTB region (Fragment 2) are atoms 1-405
>>
>> Any help with this issue or information on how to correctly construct an 
>> ONIOM input file would be much appreciated. I have attached my attempt and 
>> output files below.
>>
>> Thanks,
>>
>> Daniel
>>
>

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