what is the meaning of this?

Message

konglt · #1 Post by **konglt** » Tue Aug 30, 2005 12:18 pm

While I am relaxing a surface structure with high precision, there appears the following message and the program was terminated, anyone has some idea about this?

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

tjf · #2 Post by **tjf** » Wed Aug 31, 2005 10:09 am

Well, I suggest you do what it says and contact Georg Kresse!

#3 Post by **admin** » Fri Sep 16, 2005 12:09 pm

ZBRENT is an algorithm to search for a root of a function by Brent
method.(Numerical recipies, Section 9.3)
it may show up if the CG-algorithm (IBRION = 2) cannot find a
reasonable geometry for the next ionic step.

1) please have a look how large the last ionic steps are (XDATCAR),
a convergence to maximum forces of 0.01eV/A usually is sufficient

2) have a look whether the electronic structure of each ionic step is
converged well enough to give reasonable forces (EDIFF = 1e-04 or 1e-05)

3) if the ionic steps have become very small and you still want to
relax further, it may help to
-- switch the relaxation algorithm to the quasi-Newton algorithm (IBRION = 1)
-- set ADDGRID = .True.
please note that you need a VASP version 4.4.5 26 or newer
to use the ADDGRID option