About lattice constant problem when making Si/Ge superlattices

Dear all users,

Hi, I’ve used the LAMMPS since last year and actually I’m newbie on it.

So I have the question about what I’m making

I literally want to make the Si/Ge superlattices by using read_data file (it contains positions of Si only)

I thought it would be made by just changing appropriately some atom-IDs for Ge.

But It is known that Ge has different lattice constant(5.6579A) with Si(5.431A). And someone told me there is the function in LAMMPS that adjusts or tunes them correctly.

How can I solve this problem?