Re: About changing charge/multiplicity during QM-MM

From: Francesco Pietra (
Date: Thu Mar 28 2019 - 15:04:14 CDT

Hi William
Could you please send me a pdf of prof Truhlat paper?

On Thu, Mar 28, 2019 at 6:05 PM William Tao <> wrote:

> Hi Francesco,
> This seems to be a spin-crossing/spin-forbidden reaction.
> With conventional pure QM treatment, we need to calculate two PES of
> different spins along the reaction path and to see where two spin states
> cross.
> Please refer to Professor Truhlar's recent work "Phys. Chem. Chem. Phys.,
> 2018,20, 4129-4136" and its references.
> Hope it helps.
> Best,
> William
> Francesco Pietra <> 于2019年3月25日周一 上午2:18写道:
>> I dare posing a general question on QM-MM, surely a naive question to
>> those experienced with QM-MM (I am doing such simulations for the first
>> time).
>> I am observing a change in my metalloprotein system where apparently the
>> iron ions become bounded to other ligands, changing from FeII to FeIII. The
>> overall charge/multiplicity is not maintained, as far as I can understand.
>> Nonetheless, ORCA is repeating its SCF cycles, converging after a number of
>> cycles. I have already restarted the simulation six times for 24hr on 36
>> cores with the same settings, in particular as to the charge and
>> multiplicity, and the structure of the complex is no more changing, as far
>> as it can be judged from geometry. I can't figure out how the system
>> readjusts itself so that the QM calculation can go on.
>> Thanks for any comment
>> francesco pietra

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