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WEIMIN = [ real ]         EBREAK = [ real ]         DEPER = [ real ]

WEIMIN = 0.001 for dynamic calculation $ IBRION >=0$
  = 0 for static calculation $ IBRION =-1$
DEPER = 0.3  

These tags allow fine tuning of the iterative matrix diagonalization and should not be changed. They are optimized for a large variety of systems, and changing one of the parameters usually decreases performance or can even screw up the iterative matrix diagonalization totally.
WEIMIN = maximum weight for a band to be considered empty  
EBREAK = absolute stopping criterion for optimization of eigenvalue  
DEPER = relative stopping criterion for optimization of eigenvalue  

In general, these tags control when the optimization of a single band is stopped within the iterative matrix diagonalization schemes:

Within all implemented iterative schemes a distinction between empty and occupied bands is made to speed up calculations. Unoccupied bands are optimized only twice, whereas occupied bands are optimized up to four times till another break criterion is met. Eigenvalue/eigenvector pairs for which the partial occupancies are smaller than WEIMIN are treated as unoccupied states (and are thus only optimized twice).

EBREAK determines whether a band is fully converged or not. Optimization of an eigenvalue/eigenvectors pair is stopped if the change in the eigenenergy is smaller than EBREAK.

DEPER is a relative break-criterion. The optimization of a band is stopped after the energy change becomes smaller than DEPER multiplied with the energy change in the first iterative optimization step. The maximum number of optimization steps is always 4.

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