Building a prismatic region

Dear LAMMPS users,

For my monoclinic lattice structure, I have every details, including basis atoms, a, c and Gamma. I managed to successfully enter it into the LAMMPS. However, For making the region I did as below:

So, I read the manual and know what does each components mean. Also, I know that my lattice should have 14 atoms. So when I use the command as " region Ali prism 0 1 0 1 0 1 {bx} 0 0 " it gives me 21 atoms which isn't my desire. When I use " region Ali prism 0 7.5 0 6.5 0 3 {bx} 0 0 units box " it gives me the correct configuration. But I just chose 0 7.5 0 6.5 0 3 since it gives me the correct number of atoms ( 14 in my case ) but is there any tip on how to choose them especially to have a correct periodicity ?

Ali

Visualize your system and check where are the excessive atoms. If they are on the boundary you have to decrease slightly region size, e.g. from 1 to 0.99.

Michal

Thanks Michal. But, I think you didn’t get my point completely. If I use " region Ali prism 0 1 0 1 0 1 {bx} 0 0 " then I think it means that I will have one prismatic lattice structure, since I didn't use " units box " But it gave me 21 atom and I know that I have to have 14 atoms. Your answer will be working on " region Ali prism 0 7.5 0 6.5 0 3 {bx} 0 0 units box ". But, what about the other command?

Ali

In theory - yes, but if there are atoms exactly on a boundary of the unit cell, it is possible they will be created twice - at their original positions and shifted by a unit cell length. Changing 1 to 0.99 in the region command should prevent that. I can’t really help more, without actually seeing the unit cell.

Michal