UT theoretical chemistry code forum

Hi,

I have found two different MEPs between one initail state and two different final states using the CI-NEB method. However, it seems that there is a secondary-saddle point between the two transition states. I want to know if I can find the secondary-saddle point using the dimer method and if it is meanful to look for such a saddle point.

Thanks in advance.

Yi-An

It is of course meaningful to search for 2nd order saddle points. The dimer method as implemented in VASP will not however converge to such a saddle since it maximizes the potential energy function in only one degree of freedom while minimizing in all other. You might perhaps get some idea about the path between the your two transition states by running the NEB between the two for a few steps, especially if the path is symmetric.

Thanks a lot.

Yi-An