Reagrding ONIOM calculation

[Roshan Pudasaini]

Hello everyone,

I am trying to optimize an isotope of H  above N in HIstidine with ONIOM. I want to make two layer of calculation (high and low). In my system I want to apply high level of calculation for atom 1 to 16 which is also set constraint. Also I want to relax H (17 to 20 along H1) and apply low level of calculation in these atoms. How can I assign ONIOM calculation in input file?

Best regards,
Roshan 

[Roshan Pudasaini]

As per information provided on documentation, I want to optimize H1 using oniom method here. Since the optimization is done smoothly but while doing ONIOM calculation it is showing error message as provided in log.out file. How to solve this problem? 
Here H1 is bonded with N8 initially. I want to break bond between N8 and H1 and add H1 again to see the energy value using ONIOM.


Best regards,
Roshan

[Edoardo Aprà]

  number of electrons :                    2
  multiplicity        :                    2
  no. of electrons and multiplicity not compatible                   2

With an even number of electrons you can only have odd multiplicities.

[Roshan Pudasaini]

  number of electrons :                    2
  multiplicity        :                    2
  no. of electrons and multiplicity not compatible 

This error message appeared in the oniom section of input file. I have specified mult in dft section while optimizing H1. Here, main concern is oniom section. I am unable to find what caused problem. 

dft
  xc b3lyp
  grid medium
  mult 2
  maxiter 220
end

oniom
     high dft
     low  dft
     model 1   1 8 0.724 H1
end

[Roshan Pudasaini]

Thank you for reply.

In relax.nw,  I had assigned mult 2 in line number 46 due to odd number of electron and the optimization was converged. 

  number of electrons :                    2
  multiplicity        :                    2
  no. of electrons and multiplicity not compatible 

This error message occured during oniom calculation(83107               ONIOM LOW+MODEL) as indicated in log.out after geometry optimization. I tried to put mult 1 in oniom directory but got an error message. How can this problem be solved?


Best regards,
Roshan Pudasaini

On Thursday 25 April 2024 at 23:38:54 UTC+5:45 Edoardo Aprà wrote: