Nomenclature of the perovskite supergroup: A hierarchical system of classification based on crystal structure and composition

TLDR

A hierarchical classification of perovskite‑derived structures is derived from extensive studies of synthetic ABX₃ compounds, based on octahedral tilting, cation ordering, and site vacancies, and is applicable to many natural oxides, fluorides, hydroxides, chlorides, arsenides, intermetallics, and silicates. Applying this hierarchy to naturally occurring minerals defines a perovskite supergroup split into stoichiometric and non‑stoichiometric groups, each further subdivided into single ABX₃ or double A₂BB′X₆ perovskites. The study enumerates numerous subgroups of stoichiometric perovskites—including silicate, oxide, fluoride, chloride, and double perovskite families—and identifies a wide array of non‑stoichiometric perovskite subgroups such as hydroxide, anion‑deficient, and vacancy‑rich variants.

Abstract

Abstract On the basis of extensive studies of synthetic perovskite-structured compounds it is possible to derive a hierarchy of hettotype structures which are derivatives of the arisotypic cubic perovskite structure ( ABX 3 ), exemplified by SrTiO 3 (tausonite) or KMgF 3 (parascandolaite) by: (1) tilting and distortion of the BX 6 octahedra; (2) ordering of A - and B -site cations; (3) formation of A -, B - or X -site vacancies. This hierarchical scheme can be applied to some naturally-occurring oxides, fluorides,hydroxides, chlorides, arsenides, intermetallic compounds and silicates which adopt such derivative crystal structures. Application of this hierarchical scheme to naturally-occurring minerals results in the recognition of a perovskite supergroup which is divided into stoichiometric and non-stoichiometricperovskite groups, with both groups further divided into single ABX 3 or double A 2 BB'X 6 perovskites. Subgroups, and potential subgroups, of stoichiometric perovskites include: (1) silicate single perovskites of the bridgmanite subgroup;(2) oxide single perovskites of the perovskite subgroup (tausonite, perovskite, loparite, lueshite, isolueshite, lakargiite, megawite); (3) oxide single perovskites of the macedonite subgroup which exhibit second order Jahn-Teller distortions (macedonite, barioperovskite); (4) fluoride singleperovskites of the neighborite subgroup (neighborite, parascandolaite); (5) chloride single perovskites of the chlorocalcite subgroup; (6) B -site cation ordered double fluoride perovskites of the cryolite subgroup (cryolite, elpasolite, simmonsite); (7) B -site cation orderedoxide double perovskites of the vapnikite subgroup [vapnikite, (?) latrappite]. Non-stoichiometric perovskites include: (1) A -site vacant double hydroxides, or hydroxide perovskites, belonging to the söhngeite, schoenfliesite and stottite subgroups; (2) Anion-deficient perovskitesof the brownmillerite subgroup (srebrodolskite, shulamitite); (3) A -site vacant quadruple perovskites (skutterudite subgroup); (4) B -site vacant single perovskites of the oskarssonite subgroup [oskarssonite]; (5) B -site vacant inverse single perovskites of the coheniteand auricupride subgroups; (6) B -site vacant double perovskites of the diaboleite subgroup; (7) anion-deficient partly-inverse B -site quadruple perovskites of the hematophanite subgroup.