Well I am trying to study a monolayer system and I want to incorporate periodicity in x and y direction which I am doing in Poisson Solver (using [Parallel] Conjugate Gradient).
However for the C direction I am getting these options - Periodic, Dirichlet, Neumann, Monopole
Which one should I select for top (C) and bottom (C), if I do not want it to be periodic in that direction