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.