H4 on a circle is a theoretical toy model that allows us to explore different multireference methods. In the model, the given angle is variable. If we vary the angle and calculate the energy of the system, be it of the ground state or excited state, this could be used as a test of multireference models. The reason for this is, when the angle is near 90, the wavefunction starts to have an equal contribution from both the dihydrogen species and becomes highly multireference. This has been explored in multiple works before and remains as a system of interest.