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ERROR：FEXCF
Posted: Fri Dec 26, 2008 1:28 am
by fegg7502
When I doing a calculation for iptimization of a supercell. I was informed of the ERROR message :
ERROR FEXCP: supplied Exchange-correletion table is too small, maximal index : 3875
What should I do to solve this problem? Could anyone give some advice ? Thanks
1) i use the latest VASP 4.6
2) POTIM = 0.5, IBRION= 2
ERROR：FEXCF
Posted: Thu Jan 08, 2009 1:15 pm
by admin
usually this error indicates that the charge densities are not OK, mostly because of unphysical interatomic distances.
Please check if you have rescaled all lattice parameters properly for the supercell calculation, and if he interatomic distances are reasonable (for the input geometry, they are written in OUTCAR explicitely, if the error occurs in a higher ionic step, please check the distances from the positions of the atoms.
2) also, if the error shows up at a 1+Nth step: please check the relaxation history: POTIM might be a little too high, especially if one of the ionic steps is not fully converged electronically and the forces are not reasonable therefore (please mind that the electronic scf-procedure also stops after NELM (= 60 by default, if not set explicitely) steps, no matter if convergence is reached .