Discussion Forum

hello, I need the help of people using Periodic boundary condition for infinite system like array. i am using Comsol to simulate an array of tips (Silicon) on a substrat (Silicon), to give you an idea it's a field emitter array. i use 2D planar symmetry, i created my tip on substrat, and now i want to apply Periodic Boundary Condition ( PBC ) on the left and right edge of the rectangular domain, to simulate a 2D infinite array of tips. The simulation aim to find the norm of the Electric field at a summit of one of those tips, from 0 to 100 nm away from it. I use Electro static, the tip and substrate are at a potential of 5 V, and the 0V potential is in the air at infinity.

I have a problem : if between the two PBC edge i have 1 tip or multiples one , i don't get the same result for the electric field at the summit of the tip. the more i add tips between the 2 PBC the more the |E| field fall.

In my understanding putting 1 or 10+ tips between PBC should represent the same physical problem, an infinite array of tips, meaninig that the resulted |E| shouldn't be that much different. Especially since i use the same mesh, be it 1 or 10+ tips.

Can you explain me where i am wrong ?

Thanks a lot for reading and for answer

PS : I share a pdf with data showing that the number of tip inside the cell with PBC influence the value of Electrical field. And also 2 mph files : one with 1 tip, and an other one with 10 tips in the cell.