compute entropy/atom

Dear all,

I am interested in finding the melting temperature of a copper (Cu) island on a titanium nitride (TiN) substrate. I have attached an image of a simulation cell that I am using for this purpose with a Cu island composed of 100 red atoms on a TiN substrate with blue N and yellow Ti atoms.

Reading the paper “Entropy based fingerprint for local crystalline order” and the related LAMMPS documentation, I thought compute entropy/atom command in LAMMPS could be useful to help me find the melting temperature of the very small island in terms of entropy/atom, i.e., the temperature at which the island starts to melt by becoming significantly disordered. However, I have some questions that I really appreciate it if someone could provide me with some hints or answers.

  1. Is entropy/atom applicable to the case that I am working on at all? If yes, is it necessary that the entropy/atom commend to be computed for only Cu atoms or the whole simulation cell in my case? For example, should I use

compute 1 all entropy/atom 0.25 5.5 avg yes 3.5 local yes,


compute 1 Copper entropy/atom 0.25 5.5 avg yes 3.5 local yes ?

Is there any commend that can modify the neighbor list of this compute such that only Cu atoms are considered in the computation?

  1. If I understood the paper and the LAMMPS documentation correctly, it may be better to use the following command for my case:

compute 1 group-ID entropy/atom 0.25 5.5 avg yes 3.5 local yes

is it appropriate to use keywords avg and local yes? What values are suitable to be considered for sigma, cutoff, and cutoff2? By the way, the potential that I have predicts the following lattice constants at 0K: a_TiN = 4.2146 Å a_Cu = 3.62 Å.

  1. I am interested to investigate temperatures up to 1000K. So, is it necessary to adjust the parameters sigma, cutoff, and cutoff2 at different temperatures? If yes, is there any suggestion?

Many thanks in advance for your time and stay safe,

Reza Namakian.


I suggest you ask your Qs to the author of the compute entropy/atom
command. The person’s contact info is listed in USER-MISC/README.