Ca₁₂[Mn₁₉N₂₃] and Ca₁₃₃[Mn₂₁₆N₂₆₀]: Structural Complexity by 2D Intergrowth

Abstract

Two new calcium nitridomanganates, Ca [Mn N ] (P3, a=11.81341(3) Å, c=5.58975(2) Å, Z=1) and Ca [Mn N ] (P3‾ , a=39.477(1) Å, c=5.5974(2) Å, Z=1), were obtained by a gas-solid reaction of Ca N and Mn with N at 1273 K and 1223 K, respectively. The crystal structure of Ca [Mn N ] was determined from high-resolution X-ray synchrotron powder diffraction data, whereas single-crystal X-ray diffraction was employed to establish the crystal structure of the Ca [Mn N ] phase, which classifies as a complex metallic alloy (CMA). Both crystal structures have 2D nitridomanganate layers containing similar building blocks but of different levels of structural complexity. Bonding analysis as well as magnetic susceptibility and electron spin resonance measurements revealed that only a fraction of the Mn atoms in both structures carries a localized magnetic moment, while for most Mn species the magnetism is quenched as a result of metal-metal bond formation.

Metallic alloys at the edge of complexity: structural aspects, chemical bonding and physical properties*

“…The most complex representatives-Rh 10 Ga 17 [154] (figure 6), Cr 11 Ge 19 type [156,158,159], Mo 13 Ge 23 [156], Mn 15 Si 26 type [158,160], Rh 17 Ge 22 and V 17 Ge 31 [156,161], and Mn 27 Si 47 [157] still exhibit the same feature-a smaller but 'higher-fold' helix of a p element inside of a larger four-fold helix of a transition metal. In other words, the structures consist of two incommensurate helices and can be systematized by a number of simple primitive tetragonal blocks along the c axis (10,11,13,15, 17 and even 27) naturally leading to extremely elongated unit cells with c/a = 8 and up to 21. Most of the compounds are well ordered, not at least due to electronic restrictions-14 valence electrons per transition metal [162].…”

“…In the light of these developments, representatives of different families of compounds have been described as CMAs. Examples include metal-rich borides [8,9], carbides [10,11], and nitrides [12][13][14]. A special place in this family is reserved for Si and Ge.…”

Structural and chemical complexity of minerals: an update

“…The complexity of chemical composition and crystal structure are therefore fundamental characteristics of minerals that have high relevance to the understanding of their stability, occurrence and evolution. The universal quantitative measures of structural and chemical complexity were proposed in Krivovichev (2012, 2013, 2014; Krivovichev et al , 2018) on the basis of Shannon information theory and have been recognised as useful parameters for the analysis of various mineralogical and crystal chemical phenomena, from crystal-structure classifications to metastable crystallisation and mineral evolution (Tambornino et al , 2015; Christy et al , 2016; Varn and Crutchfield, 2016; Plášil et al , 2017; Plášil, 2018a, 2018b, 2018c; Ovchinnikov et al , 2018; Majzlan et al , 2018; Colmenero et al , 2019; Gurzhiy and Plášil, 2019; Gurzhiy et al , 2019, 2021; Hornfeck, 2020; Bindi et al , 2020; Majzlan, 2020; Mugnaioli et al , 2020; Sabirov and Shepelevich, 2021; Kaußler and Kieslich, 2021, etc.). The aim of this review is to summarise the recent findings in the field of structural and chemical complexity of minerals and to outline possible directions for its further development.…”

Li$_2$Sr[MnN]$_2$: a magnetically ordered, metallic nitride

“…Nitridomanganates show a wide variety of structures and properties: manganese may be coordinated tetrahedrally (Li 7 [Mn V N 4 ] [5]) or trigonalplanar (Li 24 [Mn III N 3 ] 3 N 2 [5], Ca 6 [Mn III N 3 ]N 2 [6], Ca 3 [Mn III N 3 ] [7], Sr 3 [Mn III N 3 ] [8, 9], Ba 3 [Mn III N 3 ] [8, 9], Sr 8 [Mn III,IV N 3 ] 3 [10]) in isolated units; ethane-like units are observed in Li [14]. Both of those semiconducting phases order antiferromagnetically; their localized magnetism originates from only a small fraction of the Mn atoms not involved in metal-metal bonding and is characterized by a large orbital contribution.…”