I am new to LAMMPS and Molecular Dynamics in general, so I am sorry if my questions are very basic.
For my masters thesis I want to study the diffusion of copper atoms on a copper (111) surface.
To start, I have created a Dimer on my copper surface in the hh (hcp-hcp) position. I want to obtain the potential energy of this position and of the Dimer in the ff (fcc-fcc) position, and the height of the energy barrier in between.
To obtain the hight of the energy barrier I tried to use the NEB command. I use a compute pe/atom command to get the potential energy of the Dimer and for every replica I create a dump file with the energy. While the potential energy difference of the start and end postition is more or less what you can find in literature, I get a potential well instead of a potential barrier in between. I guess there is something wrong with the way I think I can get the energy. Can you tell me the best way to obtain the height of the energy barrier when using the NEB command?
NEB is finding the energy as the entire system relaxes
around the dimer moving over the barrier. I'm not
clear on what you expect pe/atom to tell you unless
you are freezing everything but the dimer. NEB prints
out total energies for each replica as it proceeds thru
its 2 stages. Did those energies indicate it found a barrier
and not a well?
thank you for answering so fast.
In literature I find that there should be a potential energy barrier of about 40 meV between
those two positions. If I look at the total energies NEB prints out, I still find a well.
I guess there is some basic error in my code that I am just unable to find.
Here is my code:
boundary p p f
units metal
dimension 3
atom_style atomic
atom_modify map array sort 0 0.0
lattice fcc 3.615 orient x -1 -1 2 orient y 1 -1 0 orient z 1 1 1