[CP2K-user] [CP2K:22225] Re: ONIOM in CP2K

['daniel Storm' via cp2k]

Hi,

Sorry for the late response. I’ve done some testing and implemented what I 
could from the input file you suggested, and I got the calculation to run 
however I’m now getting different issues. The problem is during the 
optimisation. The molecule doesn’t stay together properly, Hydrogens fly 
off in random directions and other atoms can overbind into a sort of ball. 
I’ll make a list of all the things I’ve tried below.

What I’ve tried:

-          - Periodic unit cell (currently in .inp)

-          - Non-orthorhombic parameters (currently in .inp)

-          - Non-periodic unit cell

-          - Orthorhombic parameters (40 40 40, 90.0 90.0 90.0)

-          - Reduced the size of the system to just 1 cation (QM) and 1 
anion (xTB)

All of these give me the same errors. My other thought was that it could be 
an error in the basis set and ECP section or it’s in the wrong place? But 
I’m not so sure. Looking into the error messages of 
ir_tBu2PONOP_meh_oniom_27-r-3.out it crashes on FORCE_EVAL 4 which is where 
xTB is used on the QM region.

I’ve attached all relevant files again and any help would be much 
appreciated. One thing to note is that I’ve found a different approach to 
use for this project which seems to be working. I’m more looking into ONIOM 
now for interest, so there’s no problem if it can’t get sorted.

Thanks,

Daniel

On Thursday, April 16, 2026 at 2:08:46 PM UTC+1 Marcella Iannuzzi wrote:

>
> Shouldn't you pass to each FORCE_EVAL its own coordinates file?
> See the test cp2k/tests/FE/regtest-1/Solv_alch_chng_simpl.inp
> In your input it seems that each FORCE_EVAL gets the same coordinate file
> Kind regards
> Marcella
>
>
> On Thursday, April 16, 2026 at 2:40:36 PM UTC+2 dstor... at googlemail.com 
> wrote:
>
>> 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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