Perovskite Distortion Inverted: Crystal Structures of (A₃N)As (A = Mg, Ca, Sr, Ba)

Abstract

Powder samples of the compounds (A 3 N)As (A = Mg, Ca, Sr, Ba) were prepared by reacting the respective alkaline earth metal nitrides and arsenic in nickel ampoules. (Mg 3 N)As crystallizes in a cubic unit cell (space group Pm3m, no. 221) with inverse perovskite structure. The analogous compounds of calcium, strontium, and barium crystallize in an orthorhombic unit cell (space group Pnma, no. 62) as

Metal‐Rich Ternary Perovskite Nitrides

“…For the series ( A 3 N)As with A = Mg, Ca, Sr, Ba the distortion was recently analyzed to monotonically increase with rising ionic radius of the alkaline‐earth metal ion, due to the increasing size of the cuboctahedral void upon unit cell enlargement and despite the growing spatial requirement of the A 2+ ions (see Figure ). A quantification of the distortion based on a simple analysis of the local coordination polyhedra revealed the deviation from ideal cubic structure to be nearly exclusively due to distortion of the cuboctahedral surrounding of As 3– , demonstrating the rigidity of the A 6 N ‐octahedra , . An analogous situation in terms of composition, electrical properties and structural relationships is realized for the group 14 element oxides ( A 3 O) E (14) [ A = Ca, Sr, Ba, Eu, Yb; E (14) = Si, Ge, Sn, Pb] …”

“…Correspondingly, all compounds are semiconducting. The compounds of the lighter elements, P and As, in combination with lighter alkaline‐earth metals are even colored yellow, orange and red [(Mg 3 N)As, (Ca 3 N)P, (Ca 3 N)As], while those constituting of heavier elements are rather gray to black . All compounds represent diamagnetic semiconductors according to both experimental property determinations and electronic structure calculations, while findings like weak paramagnetism or slight metallic temperature characteristic of the electrical resistivity might be due to impurities and vacancies in the alkaline‐earth metal substructure .…”

Pressure-dependent electronic, optical, and mechanical properties of antiperovskite X3NP (X = Ca, Mg): A first-principles study

“…Among them, nitride antiperovskites X 3 NA with the anion N 3− located in the center of the octahedron have attracted extensive research interest due to the unique features of the nitrogen element [13−15] . So far, at least 16 experimental syntheses of X 3 NA (X 3 NE (X = Sr, Ba; E = Sb, Bi) [16,17] ; Mg 3 NPn (Pn = As, Sb) [18] ; Ca 3 NM (M = P, As, Sb, Bi, Ge, Sn, Pb, Tl) [19,20] ; and A 3 NAs (A = Mg, Ca, Sr, Ba) [21] ) have been reported. The physical properties of X 3 NA have been widely studied, including optoelectronic [22,23] , superconductivity [24−27] , magnetoresistance [28,29] , magnetostriction [30] , magnetic and magnetocaloric [31] , thermoelectricity [32,33] , negative thermal expansion [34,35] , Dirac semi-metallic characteristic [36,37] , and topological insulators characteristic [38] .…”