Hello Charmm users,

I am trying to simulate a hexagonal molecular crystal and hope to start from a unit cell. According to Charmm manual, hexagonal unit cell has a volume of V=sqrt(0.75)*a^2*c. The only possible choice is a prism with a base of parallelogram that has angle of 60-120. Therefore, if I use ' crystal build HEXA a a c 90 90 120 and crystal build noper 0 cutoff ', image operation will be purely translational like the second image in attachment. [img]

https://imgur.com/HoSOoPL[/img] However, this will not be the correct way to pack a hexagonal prism.(first pic of attactment). [img]

https://imgur.com/HoSOoPL[/img] My question is that 'what is the unit cell of hexagonal crystal? and what is the proper symmetry operation? If the unit cell strut is like what I think, how should I alter the symmetry operations(probally not use Nope 0) in order to fully mimic a hexgonal prism.