  The excitonic behavior of anisotropic two-dimensional crystals is
investigated using numerical methods. We employ a screened potential arising
due to the system polarizability to solve the central-potential problem using
the Numerov approach. The dependence of the exciton energies on the interaction
strength and mass anisotropy is demonstrated. We use our results to obtain the
exciton binding energy in phosphorene as a function of the substrate dielectric
constant.
