[lammps-users] non-orthogonal crystal

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1

Dear users,

I am very confusing how to perform the MD simulation of non-orthogonal crystal systems in LAMMPS. The problems from my side are as follows.

1) Construction of non-orthogonal crystal cell:
Although one construct the non-orthogonal crystal unit cell (ex. hexagonal crystal) using the 'lattice' command, the lattice spacing seems still the orthogonal lattice. I think that maybe I need to understand exactly the command 'region'. I understood that in order to simulate the non-orthogonal crystal one has to use the tilted simulation box (or region) which would be realized by using the 'prism' option of the command 'region', but I am not sure because the obtained simulation box is not what I expect. Could anyone guide me kindly how to construct the non-orthogonal crystal cell?

2) How to determine the lattice constants of non-orthogonal crystal lattice:
In general, to determine the lattice constants of cubic crystal, one has to perform the NPT simulation. However, LAMMPS don't have capability to perform the NPT simulation for non-orthogonal crystal. Then, is there any tricky to do such things in LAMMPS?

Thanks a lot in advance.
Chol-Jun

2

re (1): the lattice and region prism commands will create
non-orthgonal lattices - I'd just read the doc pages carefully

re (2): doing NPT with a tilted box will be added to LAMMPS
at some point - just haven't gotten to it yet ... sooner than
that we'll release the ability to minimize a tilted box - it's simpler

Steve