Editing INCAR (section)

==Finding transition states== 

A robust search for transition states starts by preconverging using a [[NEB]]. To run a NEB, please make sure you are using a VTST-modified version of VASP and put these flags on your INCAR file: 
 ionic steps:         
   IMAGES =   4     # 
   LCLIMB =   F     # 
   IBRION =   3     # 
   POTIM  =   0.011 # 
   SPRING =  -5     # 
   NSW    = 100     # Use less than 200 steps for NEBs

IBRION=3 works very well for NEBs. Do never use IBRION=2. If you have more than one local maximum, modify your initial and final states and repeat the NEB. If the initial and final states are too different, you can also do a zoom or increase the number of images. Avoid using more than 6 images. You can [[INCAR#Tips_for_efficient_electronic_relaxations|tweak EDIFF and NELMIN]] in the ''electronic steps'' section to make it run faster.    

Once the NEB is pre-converged, launch a CI-NEB: 
 ionic steps:         
   IMAGES =   4     # 
   LCLIMB =   T     # 
   IBRION =   1     # 
   POTIM  =   0.150 # 
   SPRING =  -5     # 
   NSW    =  50     # Use less than 100 steps for CI-NEB 

After 50 steps, you should have a high-quality transition state localized as the image with highest energy. CI-NEB works best with IBRION=1.  

Finally, do a [[INCAR#Frequencies_.28IBRION.3D5.2C6.29|frequencies calculation]] to check that all frequencies are real except by one that represents the transition state. 

The transition staten can be further refined by applying [[INCAR#DIIS_algorithm_.28IBRION.3D1.29|IBRION=1]] with a very small POTIM and by using the [[IDM|Improved Dimer Method]]. 

Back to [[Núria López and Group]] / [[Scripts_for_VASP]].