First, thank you very much for your previous help. I have another question to ask about NEB method. I have tried to calculate the potential barrier of Hydrogen atom in metallic bulk fcc box by displace it from its initial position to the final one. I have given it in a separate file the final coordinates, but the problem is when i have analyzed the output file I observed that the Hydrogen atom do not localized in those final coordinates ! could you help me to resolve this problem ?