VASP错误提示

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.

what these messages mean?

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ZBRENT is an algorithm search for a root of a function by Brent's method: Numerical recipies, Section 9.3
The problem in this 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





Sometimes 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 ??

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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)
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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



non-collinear: "LAPACK: Routine ZPOTRF failed(
I also ran into this problem, but I found a solution. The problem comes from doing previous calculations with a reduced k-point mesh produced by symmetry operations.

I imagine you generated the k-mesh automatically. The failed SOC run should have produced an IBZKPT file. If you peek inside it, you should see all the kpoints reported with a weighting factor of 1. If this is the case, take this file, and rename it KPOINTS. Setting ISYM=0, re-do your collinear calculation using this new file to generate your kpoint mesh. The WAVECAR and CHGCAR files you produce should be compatible with SOC calculations. Just make sure you use the exact same k-point mesh and set NBANDS = 2*collinear-run value.




ZBRENT: fatal internal in brackting
system-shutdown; contact gK immediately
this message says that during geometry optimisation no reasonable next step could be found with Brent's alg

orithm (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)
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