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 systemNow 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.