In the effective mass analyzer, one can choose type of coordinate system between Cartesian and Fractional. Fractional means in the coordinate system formed by three reciprocal lattice vectors related to the direct space lattice vectors through textbook expressions. Both reciprocal and direct space vectors can be defined in Cartesian system of coordinates, meaning that any k-vector direction can be defined in Cartesian as well. So, both options are available in QuantumATK.
