The lattice of an
antiperovskites (or
inverse perovskites) is the same as that of the perovskite structure, but the anion and cation positions are switched. The typical perovskite structure is represented by the general formula ABX3, where A and B are cations and X is an anion. When the anion is the (
divalent) oxide ion, A and B cations can have charges 1 and 5, respectively, 2 and 4, respectively, or 3 and 3, respectively. In antiperovskite compounds, the general formula is reversed, so that the X sites are occupied by an
electropositive ion, i.e., cation (such as an
alkali metal), while A and B sites are occupied by different types of anion. In the ideal cubic cell, the A anion is at the corners of the cube, the B anion at the
octahedral center, and the X cation is at the faces of the cube. Thus the A anion has a coordination number of 12, while the B anion sits at the center of an octahedron with a
coordination number of 6. Similar to the perovskite structure, most antiperovskite compounds are known to deviate from the ideal cubic structure, forming
orthorhombic or
tetragonal phases depending on temperature and pressure. Whether a compound will form an antiperovskite structure depends not only on its chemical formula, but also the relative sizes of the ionic radii of the constituent atoms. This constraint is expressed in terms of the
Goldschmidt tolerance factor, which is determined by the radii, ra, rb and rx, of the A, B, and X ions. Tolerance factor = \frac{(r_a + r_x)}{\sqrt{2}(r_b + r_x)} For the antiperovskite structure to be structurally stable, the tolerance factor must be between 0.71 and 1. If between 0.71 and 0.9, the crystal will be orthorhombic or tetragonal. If between 0.9 and 1, it will be cubic. By mixing the B anions with another element of the same valence but different size, the tolerance factor can be altered. Different combinations of elements result in different compounds with different regions of
thermodynamic stability for a given crystal symmetry.
Examples Antiperovskites naturally occur in sulphohalite, galeite, schairerite,
kogarkoite, nacaphite,
arctite, polyphite, and hatrurite. It is also demonstrated in
superconductive compounds such as CuNNi3 and ZnNNi3. Discovered in 1930, metallic antiperovskites have the formula M3AB where M represents a magnetic element, Mn, Ni, or Fe; A represents a transition or main group element, Ga, Cu, Sn, and Zn; and B represents N, C, or B. These materials exhibit
superconductivity,
giant magnetoresistance, and other unusual properties. If at least some of the metal ions are Lithium cations, the material is investigated as a possible
cathode material in
Lithium-ion batteries. Antiperovskite manganese nitrides exhibit zero
thermal expansion. == Extraterrestrial and Orbital Applications ==The physical properties of metal-halide perovskites, particularly when monolithically integrated with
thin-film chalcogenides like
CIGS, have led to significant interest in their use for space-based infrastructure and orbital data centers.
Vacuum Stability and Encapsulation While terrestrial perovskite solar cells face degradation challenges due to moisture and oxygen ingress, the high-vacuum environment of space (approximately $10^{-6}$ to $10^{-9}$ Torr) effectively eliminates these primary degradation pathways. In the absence of atmospheric humidity, the stability profile shifts toward managing thermal cycling and high-energy particle radiation. This "vacuum-native" stability reduces the need for heavy terrestrial encapsulation, allowing for thinner, lighter cell architectures.
Radiation Hardness and Self-Healing Unlike traditional crystalline silicon (c-Si) or gallium arsenide (GaAs) cells, which suffer permanent lattice displacement from high-energy proton bombardment, perovskites exhibit an inherent "self-healing" mechanism. Due to the soft, ionic nature of the lattice, displacement damage can be dynamically annealed at typical orbital operating temperatures ($40^{\circ}\text{C}$ to $80^{\circ}\text{C}$). Recent cislunar testing has demonstrated that perovskite-on-CIGS tandem cells can retain over 90% of their initial efficiency after exposure to proton fluences that would degrade traditional silicon cells by over 30%.
Specific Power and Scaling The most critical metric for megaconstellations is
Specific power. Because perovskite absorbers can be as thin as 300–500 nanometers, they can be printed onto flexible polyimide substrates. Current flight-ready prototypes have demonstrated a specific power of up to 1,960 W/kg—nearly 100x the capacity of rigid silicon arrays. This high power-to-weight ratio is considered a requirement for the deployment of megawatt-scale orbital AI data centers, where launch mass is the primary cost constraint. == Octahedral tilting ==