I ran a MC simulation for an 8-atom cell, and I saw "Supercell size: 12 12 6" in my output file. Which means that there should be 12126*8 = 6912 atoms involved in the simulation? However, in each individual MC snapshot file, it contains only 6912/4 = 1728 atoms. Why is there a factor of 1/4? Thank you.
Two explanations:
- The supercell is a multiple of the unit cell specified in lat.in not one of the ground state structures in gs_str.out
- emc2 does not output the species that cannot change ("spectator ions"), i.e. only the site that can host more than one type of atom.
Thanks. I don’t understand the first explanation. I was doing MC simulation on one of the ground state structures, how is it related to the unit cell used in my lat.in file? These two structure have different compositions. Could you please help explain a little bit more?
The MC supercell is a supercell of both the lat.in and the structure you picked in the gs_str.out file.
It is reported as a multiple of the lat.in cell because that is the natural smallest cell that would be common to any possible MC calculation you could do on that system. It’s just a convention.
BTW, the lat.in does not have a specific composition: it describes the geometry of all the sites in the lattice and their possible occupation.