IBRION=3 bulk optimization

To choose a proper value for the POTIM in case of a IBRION=3 bulk optimization, you first need to perform a frequency calculation, setting in the INCAR file

frequencies:

 IBRION =   5     #     
 EDIFF  =  1E-7   # 
 POTIM  =   0.010 #                  
 NFREE  =   2     # 

When this calculation converge you need to