fig1

Figure 1. Crystal structures of NiO with octahedral (Oct) and square-planar (Sqr) Ni coordination. The upper row shows the conventional rocksalt-like cubic cell of Oct-NiO containing four formula units (left) and the conventional PdO-like tetragonal cell of Sqr-NiO containing two formula units (right). The lower row shows the corresponding triclinic cells of Oct-NiO (left) and Sqr-NiO (right), each containing two formula units. The two-formula-unit triclinic cells were used for the structural interpolation and as the parent cells for constructing the 2 × 2 × 2 AIMD supercells. AIMD: Ab initio molecular dynamics.