Hi, Dr. Benjamin, I am very interested in this TI method, but I have some uncertain parts to apply this method in LAMMPS. In the simulation section, I am not sure if the wall particles are included in the system. During the changing of the wall, the total particle number is maintained or is changing? The TI scheme is well explained, however, for the implement in MD. I wish I could get some suggestion. From bulk sample to system with structureless wall, the wall particles are inserted together with bulk particles (i.e.only by modifying the potential to change the wall) or some bulk particles are replaced by wall particles? In the second step, how to switch off the flat wall and how to switch on the structured wall in simulation?
Really appreciate if you could give me some suggestion! Thanks!
Article Wall-liquid and wall-crystal interfacial free energies via t...
Hi Dr. Wan Shou,
In the first step you go from bulk to structureless flat wall, given by Eq. 17. The calculation of the thermodynamic integrand and derivative is given in Eqs. 23 and 24, respectively. Upto here the total number of particles is N_c (or N_l), which are either all crystal or all liquid particles.
When the structured wall is introduced the total number of particles is N=N_l (or N_c)+ N_sw, where N_w is the total number of structured wall particles, so yes the total number of particles are changing but since the structured wall is like an external field, the total number of particles comprising what we call the system (which is the crystal or the liquid phase) remain the same i.e. N_c or N_l as the case maybe. So what we do is insert new particles which are rigidly (not moving) attached to fcc lattice lattice sites with a particular lattice constant. We insert between 3-6 layers of such particles (along the z- direction). Fig.6 makes this clear.
The scheme to switch off the flat wall and switch on the structured wall is given by Eqs. 31-33. During this procedure the position of the layer of structured wall particles facing the liquid is made to coincide with the position of the flat wall (along the z-direction) , which is the position of the Gibbs dividing surface.
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