Start state and end state

zhangj · Post by **zhangj** » Fri May 25, 2007 6:10 am

Dear Sir,

In NEB method, if I get one image between initial state and end state, can I devide the MEP into two sections? I mean the first section is from initial state to image 1 (which is the new final state); and the second section is from image 1 (which is the new inital state) to final state. Then the new images are interpolated into the two section, respectively. Or during each NEB calculation (for example, in the first calculation, only one image is interpolated, and then more images are interpolated), the initial state and the final state must be consistent.

Many thanks.
Zhang Jia

Post by **graeme** » Mon May 28, 2007 3:50 pm

If you have an intermediate structure, you can generate one band between the initial and intermediate states and a second between the intermediate and final states. Then, by renumbering the directories, you will have a single initial band from initial to final through the intermediate.

Remember to use a small initial time step if the spacing of images is quite different in the two sub-bands.

zhangj · Post by **zhangj** » Wed May 30, 2007 8:07 am

Dear Sir,

Thank you for your reply.
Another question, can I calculate the two pathways ( 1. from start state to intermediate structure, 2. from intermediate structure to final state) respectively, then combine the two pathway together to get MEP?

Thanks again

Zhang Jia

Post by **graeme** » Wed May 30, 2007 2:34 pm

No. There are two problems with doing that. First, the intermediate image will not be relaxed, and second, your fixed endpoints must be on the minimum energy path (MEP). If the initial and final points are minimized, they are on the MEP, and then all images between them need to be relaxed collectively to find the MEP.