I am trying to simulate an infinite 2D triangular lattice in Comsol but I am confused that how should I use periodic floquet boundary conditions on the unit-cell. A unit cell that I am using is given below:
It has $6$ sides, $L1,L2,...,L6$. In the case of a square lattice, we simply just select floquet boundary conditions on both pairs of opposite sides because $k_x$ and $k_y$ are parallel to those sides.
Now, the pair of opposite sides (i.e. L1 and L4, L2 and L5, and L3 and L6) are not parallel to the $k$ vectors. How do we define boundary conditions now?
(I am trying to calculate the band structure on $\Gamma$, $K$ and $M$ points which are defined on this orthogonal $k_x$, $k_y$ axis.)