I want to replace a new kind of atoms

Dear lammps user,
I had a box full of alloy (Au-50%Ag) then deleted the atoms of Au.
Now, I want to replace another kind of atom instead of those empty places. How can I do it? Bcause, if I use the create_atoms command, it will fill the box completely while I want it to fill just blanks.

Thanks in advance,

Why did you delete those atoms? If you want to replace them with another type, can’t you just redefine the mass and the interaction potential of the same type with new values?