Once the equilibrium placement is found, the next step of the algorithm is to find a unit cell. In general, a cell is a parallelepiped whose three axes (⃗ a, ⃗ b, ⃗ c) are linearly independent translations that constitute symmetries of the graph. Such translations will be called valid translations. Another representation for this cell is the matrix A whose columns are respectively ⃗ a, ⃗ b and ⃗ c.