On Mon, Sep 7, 2015 at 1:13 PM, Kshatresh Dutta Dubey <kshatresh.gmail.com>
wrote:
> Dear Users,
>
> I have to assign spin=5 in QM/MM calculations using DFTB as QM/MM
> interface. How can I do it? If I am using qmcharge= -1, spin = 5, it is
> showing error as :
> parameter QMMM: (Spin multiplicity) has value 5
> This is outside the legal range
> Lower limit: 1 Upper limit: 1
> The limits may be adjustable; search in the .h files
>
> I am using Amber 14.
>
> I will be thankful for all suggestions. Thanks in advance.
>
To my knowledge none of the semiempirical models in Amber support
multiplets. You will probably have to go through the external QM interface
and run a calculation with a program that *does* support non-singlet spin
states.
I'm not an expert with high-level quantum mechanical calculations, but with
high spins (and a spin multiplicity of 5) may require multireference
treatments -- you should consult the existing literature to see how people
have addressed your problems in the past. This could be a potentially
*very* challenging problem.
HTH,
Jason
--
Jason M. Swails
BioMaPS,
Rutgers University
Postdoctoral Researcher
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Received on Mon Sep 07 2015 - 11:00:03 PDT
