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Re^4: Optimization of conical intersection with penalty function method: how to control the gap?


Dear Alex,

Thanks for your answer! I wonder how much should I increase the B parameter to converge to a conical intersection with a smaller gap (0.0001)? With the default value of B (3.5) the gap is ~0.003.

Best regards,

On Sat Oct 22 '16 11:23pm, Alex Granovsky wrote
>Dear Evgeniy,

>SHIFT0 and SHIFT variables are primary used by Lagrange multiplier-
>based code.

>SHIFT can be used with penalty function based code but has very
>little impact on the energy gap when gap is large and shift
>is small. It is intended to trace rather large differences between
>states like 0.1 or 0.05 Hartree.

>Kind regards,
>On Sat Oct 22 '16 7:39pm, GrEv wrote
>>Dear Alex,

>>Thanks very much for your reply.
>>Just a curios question, what does the SHIFT option do?

>>Best regards,

>>On Sat Oct 22 '16 6:00pm, Alex Granovsky wrote
>>>Dear Evgeniy,

>>>there is no direct control over the energy gap for penalty-based CoIn
>>>optimization procedures. The gap can be controlled indirectly using
>>>parameters defining a penalty function. The larger is the "strength"
>>>of penalty function the smaller will be the gap. With Firefly, the
>>>strength is controlled by the parameter B of $mcaver group.

>>>Kind regards,
>>>On Sat Oct 22 '16 11:50am, GrEv wrote

>>>>I am doing optimization of the minimum energy conical intersection using the penalty function method, with the following input (from the manual, p. 176) :

>>>>$STATPT OPTTOL=0.00005 NSTEP=500 method=qa trmax=0.05 dxmax=0.05
>>>> HSSEND=.f. $END

>>>>Using this input I found a conical intersection (CoIn), with the final gap between the states of 0.003. I'd like however to have a smaller gap, let's say 0.0001. How this could be done. I've tried to use the SHIFT option in $MCAVER, setting SHIFT=0.0001. It however didn't do the job. I got a CoIn with almost the same gap as before.
>>>>Many thanks!


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