I have two planes stacked on top of each other. Each plane looks like this:
Each plane, however, has a different hexagonal side length (the first plane has hexagons with side length $a$ and the second plane has length $b$).
I am trying to figure out what angle I most rotate the $a$ plane in order to make each "unit cell" periodic. In other words, each ring in each plane should correspond to a ring below it, just with a different rotation.