[lammps-users] enquire on defining lattice

The itype arg in the create_atoms command is to assign atom
types to the basis atoms setup by the lattice command. Say you
put 2 basis atoms per units cell in your lattice. Each can be
any "type" you want in LAMMPS. Same as the types you
define for atoms in a data file read by the read_data command.

So the itype settings let you say the first basis atom will
be type 3, and the 2nd basis atom will by type 5, for example.


Thank you, Sir. Now I understood what itype arg means. The 2 basis atom in the unit cell are the same, so itype=1.

I have 1 query on defining basis atom using lattice command. If my system is a simple cubic or space group = P 1, then I will use lattice … custom … basis 0 0 0 . However, my complicated organic crystal has a space group = P 1_bar or P -1, which implies that the second basis is in an inversion position to the first basis. If I were to use lattice with custom command, then I’ll define basis 0 0 0 for the first basis, but what fraction should I use to define the position for the second basis?

Thank you very much.