My Community

After 20 ionic steps, the surface relaxation calculation is automatically stopped. Error massage is attached as below:

20 F= -.68277137E+02 E0= -.68272811E+02 d E =-.140470E-01 mag= 11.1515
curvature: 0.00 expect dE= 0.219-310 dE for cont linesearch 0.213-310
ZBRENT: fatal internal in brackting
system-shutdown; contact gK immediately

what really happened? Anybody encounted the same problem before?

Tiger-paw

This error occurs if the next ionic step cannot be estimated with the ZBRENT
algorithm (the algorithm is documented in the Numerical Recipies).

--) you seem to be at the energy minimum of the parabola already (curvature=0.00,....):
For most applications a geometry can be regarded as converged if the maximum
remaining forces are less than 0.01 eV/AA, therefore
EDIFFG = -1e-02
is a reasonable choice.
Please check the forces of your last ionic step (in OUTCAR)

--) Please also have a look at the XDATCAR file: If the ionic step sizes have become very small already, the GC algorithm may fail to extrapolate the next step (---> switch to IBRION = 1 instead)

--) If you want to increase the accuracy of the calculated forces even more, set ADDGRID = .True. in INCAR
Please have a look into the online manual
http://cms.mpi.univie.ac.at/vasp/vasp/node147.html
for further information on the ADDGRID input parameter.