[Wien] way to confirm stable/transition structures

[tasaka at affinity-science.com]

Hi,

thank you for the detailed explanations.

> this is always the case which are well known although often omitted in
> simple textbooks. I am 99.8% certain that MSR1a will also not be
> trapped in a saddle point although there is currently no analytic
> proof of this.

I agreed, it was a help to me!

With best regards,
Tomo

----- Original Message -----
> This is a slightly complicated question. What you sent is a transition
> state, mathematically a saddle point. You are asking if within MINI
> (and/or MSR1a) you can get trapped in one.
> 
> I can only answer for PORT & MSR1a. If you start a little away from a
> saddle point, and there are no other issues such as problems with
> touching RMTs or inconsistent forces, the program will converge to a
> true local minimum. There are some standard traps that ensure that
> this is always the case which are well known although often omitted in
> simple textbooks. I am 99.8% certain that MSR1a will also not be
> trapped in a saddle point although there is currently no analytic
> proof of this.
> 
> A caveat. If you were to start at the exact saddle point (or very
> close to it) the mini code may decide that you have already converged
> and stop without checking. This is because the convergence criteria
> are just that the forces are small, not that the Hessian is positive
> definite (i.e. a local minimum).
> 
> Another caveat. If you have a soft mode distortion away from the
> saddle point the code might also be fooled into thinking it has found
> a minimum whereas in reality it has not. PORT is quite good in
> avoiding this; MSR1a not quite so good for a number of reasons.
> 
> And yet a third one. It is possible to force a saddle point using
> symmetry, for instance if you added a z-axis mirror.
> 
> If you are concerned whether you have got trapped in a saddle point
> because you started there, move the atomic positions a bit and rerun.
> 
> N.B., a different question is how to find a saddle point/transition 
state.
> 
> On Fri, Oct 5, 2012 at 4:55 AM, tasaka at affinity-science.com
> <tasaka at affinity-science.com> wrote:
> > Hello,
> >
> > In MINI calculation, a relaxed structure is depend on initial 
structure
> > in general. so, sometimes it might arrive to the transition 
structure.
> > for example, please find the attached structure file.
> > for that case, how do we confirm the obtained structure whether
> > transition or stable structure, especially in wien2k-code?
> >
> > sorry if it's a silly question, but any information would be 
appreciated.
> >
> > With best regards,
> > Tomo
> 
> 
> 
> -- 
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu 1-847-491-3996
> "Research is to see what everybody else has seen, and to think what
> nobody else has thought"
> Albert Szent-Gyorgi
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