Synthesis and crystal structures of novel LaOAgS-type alkaline earth – Zinc, manganese, and cadmium fluoride pnictides

Layered Compounds BaFMgPn (Pn = P, As, Sb, and Bi), Transition-Metal-Free Representatives of the 1111 Structure Type

“…Our prediction and successful synthesis of two transition metal-free tetrelides, BaFAlSi and BaFAlGe, prompted us at investigation of some other valence isoelectronic systems, the most likely representatives being compounds involving [Mg 2 Pn 2 ] 2– (Pn = P–Bi) slabs observed in a series of ternary CeFeSi-type group 1–group 2 pnictides. We also note that the Mg–Pn distances in structurally characterized NaMgAs, NaMnSb and KMgPn (Pn = P, As, Sb, and Bi) are rather close to the Cd–Pn ones observed in BaFCdPn, , suggesting the existence of BaFMgPn compounds. The relatively large size of the mackinawite-type slabs makes the [Ba 2 F 2 ] 2+ litharge-type slabs the best candidates for their counterparts; as in the previous cases, possible Sr–F and Ln–O analogs were also considered.…”

“…Following the trend in atomic radii, the next representative, BaFMgAs, exhibits a longer distance d(Mg−Pn), which results in a slight flattening of the FBa 4 tetrahedra while the MgAs 4 counterparts are now almost regular. The heavier analogs, BaFMgSb and BaFMgBi, are characterized by increasingly flattened FBa 4 but elongated MgSb 4 and MgBi 4 tetrahedra since d(Mg−Pn) > d(Ba−F).The same trend is observed in the crystal structures of other BaFTPn (T = Zn, Mn, and Cd) compounds 26. The values of α 2 and α 4 of 119.8°and 104.6°in BaFMgBi are very close to those observed in the structure of BaFI; 47 however, they are probably rather close to the tolerance limit for the distortion of the FBa 4 tetrahedra.…”

“…Compared to the previously reported cases, − , the synthesis of BaFMgPn type compounds is more complex due to high reactivity and volatility of magnesium above its melting point (∼920 K) and extreme air and moisture sensitivity of the target products. Although no thermal effects were observed for all four compounds up to 1273K, the synthesis temperature had to be decreased when passing from BaFMgP (1223K) to BaFMgBi (973 K).…”

“…Atomic charges were calculated in accordance with R. Bader’s quantum theory of atoms in molecules (QTAIM) using the DGrid4.6 package and Bader code, − utilizing ELK wave functions or VASP charge density, respectively, as inputs. The estimations of structure stabilities were made according to the approach established in ref by comparing calculated total energies of quaternary compounds and their precursors. The electron localization function (ELF) was calculated by the internal VASP routine.…”

“…Based on the chemical composition of the litharge part, its representatives can be separated into several groups. Most numerous are oxide compounds containing [M 2 O 2 ] n + (M = Th, U–Pu for n = 4, and Bi, La–Er for n = 2) slabs; − fluorides containing [M′ 2 F 2 ] 2+ fragments (M′ = Ca, Sr, Ba, or Eu − ) are less common mostly due to the smaller variety of the divalent cations; hydrides are the rarest, and there exists only one unique nitrogen-based compound, ThN 1– x O x FeAs …”