Within all relaxation algorithms (IBRION=1,2 and 3) the parameter POTIM should be supplied in the INCAR file. For IBRION0, the forces are scaled internally before calling the minimization routine. Therefore for relaxations, POTIM has no physical meaning and serves only as a scaling factor. For many systems, the optimal POTIM is around 0.5. Because the Quasi-Newton algorithm and the damped algorithms are sensitive to the choice of this parameter, use IBRION=2, if you are not sure how large the optimal POTIM is.

SYSTEM = Mg-hex
ENCUT = 250
ISTART = 0; ICHARG = 2
ISMEAR = 1; SIGMA = 0.2
NSW = 60; IBRION = 2
ISIF = 3
POTIM = 0.2
EDIFF = 1E-6; EDIFFG = -1E-3
PREC = Accurate

Originally posted by stractor at 2010-12-18 10:52:01:
我一般使用默认值POTIM=0.5。而且IBRION=2的算法比较可信。
驰豫的时候POTIM的设置只会影响运行的效率，不会对结果又明显的影响。
不用管它，默认值很不错。

[ Last edited by stractor on 2010-12-18 at 1 ...