what does "ZBRENT" mean?

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Kertick

what does "ZBRENT" mean?

#1 Post by Kertick » Tue Oct 17, 2006 4:14 am

Hi,
I relaxed a molecular system with 39 atoms, using ISMEAR = 0, SIGMA = 0.02, IBRION = 2, POTIM = 0.5.
Then I found some messages like
" ZBRENT: increasing intervall"
" ZBRENT: bracketing found"
" ZBRENT: interpolating"
" ZBRENT: can't locate minimum, use default step"
at the end of some ionic steps in the log file.

Could anyone tell me what these messages mean?
Thank you in advance.

Sinderely,
Kertick
Last edited by Kertick on Tue Oct 17, 2006 4:14 am, edited 1 time in total.

admin
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what does "ZBRENT" mean?

#2 Post by admin » Wed Oct 18, 2006 2:23 pm

ZBRENT is an algorithm search for a root of a function by Brent's method: Numerical recipies, Section 9.3
The problem in your case might be that the Conjugate Gradient algorithm (IBRION=2) is not suitable for very small corrections of the atomic positions if your system has almost reached equilibrium (please have a look at XDATCAR to check the size of the relaxation steps done before the ZBRENT warnings show up). Usually it is sufficient to converge a system up to maximum remaining forces of about 0.01eV/A (EDIFFG=-0.01).
please try one of the following:
1) choose a different algorithm for ionic optimization (IBRION=1)
2) set ADDGRID=.True. in INCAR (only for vasp releases 4.4.5 and newer)
Last edited by admin on Wed Oct 18, 2006 2:23 pm, edited 1 time in total.

happy
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what does "ZBRENT" mean?

#3 Post by happy » Wed Apr 28, 2010 7:42 am

ADDGRID=.True. dosn't work.
Last edited by happy on Wed Apr 28, 2010 7:42 am, edited 1 time in total.

happy
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what does "ZBRENT" mean?

#4 Post by happy » Wed Apr 28, 2010 7:53 am

ADDGRID=.True. dosn't work.
Last edited by happy on Wed Apr 28, 2010 7:53 am, edited 1 time in total.

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