Fatal Internal in Bracketing

Problems running VASP: crashes, internal errors, "wrong" results.


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sudhakar

Fatal Internal in Bracketing

#1 Post by sudhakar » Thu Feb 23, 2006 2:05 pm

Hi

Sometimes my calculations crash with the following message in standard output

ZBRENT: fatal internal in brackting
system-shutdown; contact gK immediately

The calculations run perfectly fine for sometime ans then suddenly they just die with the above error.

What might be the cause of such an error ??

Thanks a lot
Last edited by sudhakar on Thu Feb 23, 2006 2:05 pm, edited 1 time in total.

admin
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Fatal Internal in Bracketing

#2 Post by admin » Fri Feb 24, 2006 12:35 pm

this message says that during geometry optimisation no reasonable next step could be found with Brent's algorithm (linear bisectioning)
please check the following
1) is the system converged already? (look at the forces in OUTCAR, especially if you use the total energy change as congvergence criterium for ionic optimisation)
2) if not: is each ionic step converged electronically ( this is needed to obtain reasonable forces)
Last edited by admin on Fri Feb 24, 2006 12:35 pm, edited 1 time in total.

linglin

Fatal Internal in Bracketing

#3 Post by linglin » Wed Sep 24, 2008 1:24 am

Well, I encounter the same problem when I optimize the geometry. I set EDIFFG=-1E-2. And every SCF is converged. But in the last SCF non-local-force acting on ions is -.178E-14 0.000E+00 0.000E+00; it seems not small enough,right? I see the total drift is 0.000063 -0.000007 -0.000005.
I don't know whether the optimization is OK ended.
Or what parameter do I need to let the convergence continue?
Last edited by linglin on Wed Sep 24, 2008 1:24 am, edited 1 time in total.

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Fatal Internal in Bracketing

#4 Post by admin » Wed Sep 24, 2008 1:47 pm

sometimes, if the calculation is already highly converged, vasp cannot interpolate the next step to within the numerical accuracy because it simply would be so small. (this behaviour is machine-dependent). If you have used IBRION=2, it may help to switch to IBRION=1 and set ADDGRID=.true. in addition
Last edited by admin on Wed Sep 24, 2008 1:47 pm, edited 1 time in total.

linglin

Fatal Internal in Bracketing

#5 Post by linglin » Thu Sep 25, 2008 1:03 am

Thx a lot.
Last edited by linglin on Thu Sep 25, 2008 1:03 am, edited 1 time in total.

gpkmohan

Fatal Internal in Bracketing

#6 Post by gpkmohan » Wed Oct 08, 2008 10:28 am

As said by the head admin. i have solved my NEB optimization, by switching from IBRION=2 [conjugate grad.]to IBRION=1[q-N]. thnx
Last edited by gpkmohan on Wed Oct 08, 2008 10:28 am, edited 1 time in total.

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