Figure 1.

Zero-field energy spectra of four Ni${}^{2+}$ coordination complexes. Subfigures (a–d) represent the cases of octahedral, square planar, trigonal bipyramidal and tetrahedral geometry, respectively. The values of all parameters are given at the end of Section 2.1. At the given energy scale, each line represents a set of sublevels. The bolder a line, the larger the number of sublevels; see the numerical representation of these spectra in the Supplementary materials, Section S6.