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Efficient relaxation from a pre-converged starting guess

Close to a local minimum the variable-metric (RMM-DIIS algorithm) is most efficient. INCAR file (for briefness the recommended setup is lacking, see Sec. 6.2.3):

NELMIN = 8     #   do a minimum of ten electronic steps 
EDIFF  = 1E-5  #   high accuracy for electronic groundstate
EDIFFG = -0.01 #   small tolerance for ions 
NSW    = 20    #   20 ionic steps should do
MAXMIX = 80    #   keep dielectric function between ionic movements

IBRION =  1    #   use RMM-DIIS algorithm for ions
NFREE  =  10   #   estimated degrees of freedom of the system
Now very accurate forces are required (EDIFF is small). In addition a minimum of eight electronic steps is done between each ionic updated, so that the electronic groundstate is always calculated with very high accuracy. NELMIN=8 is only required for systems with extreme charge sloshing which are very hard to converge electronically. For most systems values between NELMIN=4 and NELMIN=6 are sufficient.

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