Über quaternäre Oxoplumbate(IV). Zur Kenntnis von Rb2Li14[Pb3O14] und Cs2Li14[Pb3O14]

On Quaternary Oxoplumbates(IV). On the Knowledge of Rb₂Li₁₄[Pb₃O₁₄] and Cs₂Li₁₄[Pb₃O₁₄] For the first time, Rb₂Li₁₄[Pb₃O₁₄] and Cs₂Li₁₄[Pb₃O₁₄] have been prepared by heating of mixtures of Li₂O, β-?PbO₂”? and Rb₂PbO₃, Cs₂PbO₃ respectively with Li:Pb:A = 14:3:2, (A = Rb, Cs). [Ag-cylinders, sealed under vacuum in Duran-glass ampoule, 590 and 550°C, 40 d, powder (650°C, 200 d, single crystals of Rb₂Li₁₄[Pb₃O₁₄])]. Rb₂Li₁₄[Pb₃O₁₄] is nearly colourless with ivory nuance, Cs₂Li₁₄[Pb₃O₁₄] is pale yellow. According to powder and single crystal investigations, both are isotypic with K₂Li₁₄[Pb₃O₁₄]. Structure refinement of Rb₂Li₁₄[Pb₃O₁₄]: 1015 symmetry independent reflexions, four-circle-diffraktometer PW 1100 (Fa. Philips), ω-scan, MoKα, R = 5.73%, R_W = 5.33%, absorption not considered, space group Immm with a = 1284.71(9), b = 793.90(4), c = 727,35(5) pm, d_x-ray = 4.99 g · cm^?3, d_pyc = 5.01 g · cm^?3, Z = 2. Cs₂Li₁₄[Pb₃O₁₄]: a = 1295.28(12), b = 796.69(8), c = 732.44(7) pm, d_x-ray = 5.31 g · cm^?3, d_pyc = 5.28 g · cm^?3, Z = 2. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Effective Ionic Radii, MEFIR, are calculated.     

Thio- und Selenomercurate(II). K6[HgS4], K6[HgSe4], Rb6[HgS4] und Rb6[HgSe4]

Thio- and Selenomercurates(II). K₆[HgS₄], K₆[HgSe₄], Rb₆[HgS₄] and Rb₆[HgSe₄] We prepared by annealing intimate mixture of pure samples of K₂S, K₂Se, Rb₂S, and Rb₂Se with HgS or HgSe [360–380°C, 7d, Duran-glass-seal with Argon] with hexagonal Na₆ZnO₄ isotypic new mercurates: K₆[HgS₄] [bright citronic yellow a = 9.98₅, c = 7.65₂ Å], K₆[HgSe₄] [light orange yellow a = 10.3₆, c = 7.88₃ Å], Rb₆[HgS₄] [bright yellow a = 10.3₄, c = 7.94₂ Å], Rb₆[HgSe₄] [orange-red a = 10.7₂, c = 8.19₂ Å]. The crystal structure of K₆ Hgs₄ is elucidated by using diffractometer data of single crystals: P63mc, C⁴_6v, it is R = 6.6% for 304 reflexes [h k o–h k 4, anisotropic refinement MoKα]; for position and parameters see text d_rö = 2.83₅, d_pyk = 2.99 g · cm^?3. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, are calculated and discussed.     

Über Oxoplumbate(IV).IDie Kristallstruktur von Rb2PbO3

Rb₂PbO₃ [single crystals, 244 (hkl)] crystallises orthorhombic [D? Pmcn] with a = 10.8, b = 7.49, c = 5.98 Å [Z = 4, d_pyk = 5.69, d_rö = 5.80 g · cm^?3], Rb in 8(d) Pb in 4 (c), O_I in 4 (c). The parameters are shown in table 2. The MADELUNG Part of Lattice Energy of Rb₂RBO₃ and structurally related models are calculated and discussed in detail. Characteristic for the structure are ldimensional chains consisting of alternatingly directed pseudo-tetragonal pyramids, ∞¹[PbO₁O_4/2], connected via common basis edges.     

“Fragmentierung” und “Aggregation” bei Bleioxiden Über das Oligooxoplumbat(IV) K2Li6[Pb2O8]

“Fragmentation” and “Aggregation” on Lead Oxides. On the Oligooxoplumbate(IV) K₂Li₆[Pb₂O₈] For the first time, the dinuclear Oxoplumbate(IV) K₂Li₆[Pb₂O₈] has been prepared as transparent colourless single crystals by heating mixtures of K₂PbO₃, Li₂O, and “PbO₂” with K:Li:Pb = 1:3:1 e. g. [Ag-cylinders, sealed under vacuum in Supremax-glass ampoule, 660°C, 120 d]. The structure determination verifies the space group P1 with a = 6.9720(9), b = 5.9252(6), c = 5.9312(7) Å, α = 88.05(1)°, β = 107.94(1)°, γ = 107.30(1)°; d_x = 4.95 g · cm^?3, d_pyk = 4.91 g · cm^?3; Z = 1, [2107 symmetry independent hkl, fourcircle-diffractometer Philips PW 1100, ω—2Θ—scan, MoKα, R = 5.07%, R_w = 4.59%, absorption not considered]. The structure is characterized by the group [Pb₂O₈] — two edge connected (equatorial/apical) trigonal bipyramids — that is observed for the first time. Several ways of synthesis are given. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Effective Ionic Radii, MEFIR, are calculated.     

Zur Konstitution von ‚KPbO2’︁

On the Constitution of ‘KPbO₂’ Transparent, orangered single crystals of K₂Pb₂O₄ have been obtained by heating mixtures of K₂O₂ and PbO (K:Pb = 1:1) [Ag-cylinders, 560°C, 40 d, after cooling (15°C/h)]. The space group is P1 , a = 1295.94(9), b = 753.35(7), c = 697.12(8) pm, α = 118.00(1)°, β = 106.15(1)°, γ = 93.44(1)°, Z = 4, d_x = 6.573 und d_pyk = 6.54 g · cm³. The structure is characterized by rutilanalogous chains of edge-connected [PbO₆] octahedra along [001] according to [PbO_4/2O_2/1] = PbO₄. On both sides of such a chain there are respectively three O^2?, which belong to two octahedra, alternating capped with Pb²⁺ or not capped, corresponding to [PbO₄]Pb₂[PbO₄]□₂… = Pb₂O₄. Those capped chains are held together by K(1)…K(4), each of them with C.N. 6. The order of the chains corresponds to the motive of a closest packing. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Das erste Oxoplumbat(II) mit Inselstruktur: K4[PbO3]

The First Oxoplumdat(II) with Island Structure: K₄[PbO₃] For the first time K₄PbO₃ has been prepared as colourless powder and transparent single crystals, respectively. K₄PbO₃ crystalizes orthorhombic, space group Pbca-D, a = 6.54₃, b = 11.40₅, c = 18.70₉ Å, Z = 8. d_rö = 3.99, d_pyk = 3.98. For 1040 independent reflextions we find R = 9.6%. Parameters see text. There are isolated PbO₃ groups, with symmetry approximately C_3v, which are ordered in a very complicated manner and connected by K⁺ ions forming layers. The Madelung Part of the Lattice Energy, MAPLE, and Effectiv Coordination Numbers, ECoN, these by means of Mean Fiktive Ionic Radii, MEFIR, are calculated and discussed.     

K2Zn3O4 und Rb2Zn3O4, zwei neue Oxozincate mit Gerüststruktur [1]

K₂Zn₃O₄ and Rb₂Zn₃O₄, Oxozincates with Framework Structure For the first time single crystals of K₂Zn₃O₄ were obtained by heating mixtures of the binary oxides (K: Zn = 2.2:3) in sealed Ag- or Pt-capsules at 800°C (5 w). Powder of this colourless and moisture-sensitive oxide was prepared analogously at 500°C. It crystallizes monoclinic, space group C2/c with a = 1482.7(2), b = 637.3(1), c = 571,9(1) pm, β = 102.79(1)°, Z = 4, d_x = 4.265 g/cm³, d_pyk = 4.00 g/cm³. The crystal structure was determined from four-circle diffractometer data (MoKα, 730 unique hkl) and refined to R = 5.9%, R_w = 6.4%. It shows a Zn₃O₄ framework which consists of SiS₂-like chains [ZnO_4/2] connected by puckered layers of [ZnO_3/3]. The crystal structure can be derived from a cubic closet packing of O^2? and K⁺. Effective Coordination Numbers and the Madelung Part of Lattice Energy (MAPLE) are calculated. Rb₂Zn₃O₄ was prepared from the binary oxides at 400°C (colourless hygroscopic powder). According to powder data it crystallizes isostructural to K₂Zn₃O₄ with a = 1523.5(4), b = 649.8(2), c = 574.0(2) pm, β = 101.43(3)°, Z = 4, d_x = 5.141 g/cm³, d_pyk = 5.20 g/cm³.     

Zur Kristallstruktur von Li8PbO6 [1]

On the Structure of Li₈PbO₆ For the first time single crystals of Li₈PbO₆ have been prepared by heating of mixtures of Na₂PbO₃ and Li₂O [Ag-cylinders, 650°C, 150 d]. The structure [382 I₀(hkl), four circle diffractometer PW 1100, ω/2Θ-scan, MoKα, R = 3.07%, R_w = 3.00%, space group R3 ; a = 555.09(4), c = 1564.13(17) pm, D_x = 4.28 g · cm^?3, D_pyk = 4.24 g · cm^?3, Z = 3] is characterized by the motive of a hexagonal-closed O^2? packing. Half of the octahedral sites are occupied by Pb⁴⁺ and Li⁺ and half of the tetrahedral sites only by Li⁺. The Madelung Part of Lattice Energy, MAPLE, and the Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated.     

Zur Kenntnis der Oxopalladate der Alkalimetalle [1]

On Oxopalladates of Alkali Metals According to X-ray data of single crystals there are: Na₂PdO₂ (yellow rod-shaped crystals) orthorhombic, a = 3.07₇, b = 10.35₉, c = 8.35₁ Å, Z = 4; d_x = 4.60, d_pyk = 4.6₃ g · cm^?3. ?K₂PdO₃”? (black square prism) orthorhombic, a = 6.20₂, b = 9.21₉, c = 4× 11.37₂ = 45.4₈ Å, Z = 24, d_x = 3.60, d_pyk = 3.5₀ g · cm^?3, and ?K₆PdO₄”? (orange square prism) orthorhombic (pseudotetragonal), a = b = 12.36₈, c = 13.59₃ Å, Z = 8, D₂⁴—P2₁2₁2₁. ?Rb₂PdO₃”? (black) is isostructural (Guinier data) to ?K₂PdO₃”?, a = 7.35₄, b = 9.60₅, c = 11.58₆ Å, d_x = 4.58, d_pyk = 4.4₇ g · cm^?3. Na₂PdO₃ exists in another reddish brown form, isostructural to Li₂MnO₃ (C_2h⁶—C2/c), a = 5.37₄, b = 9.30₉, c = 10.78₉ Å, β = 99.5°, Z = 8, d_x = 5.00, d_pyk = 4.7₃ g · cm^?3.     

Neue Oxozincate der Alkalimetalle: Rb2[ZnO2] und Cs2[ZnO2]

New Oxozineates of Alkali Metals: Rb₂[ZnO₂] and Cs₂[ZnO₂] Colorless single crystals of the hitherto unknown Rb₂[ZnO₂] (a = 9.55₈, b = 6.33₅, c = 15.91 Å, β = 118.6°, z = 8, d_pyk = 4.11, d_rö = 4.21 g · cm^?3) and Cs₂[ZnO₂] (a = 9.85₁, b = 6.61₉, c = 16.26 Å, β = 116.8°) have been prepared, which crystallize monoclinic, P2₁/c – D. (For parameters see text.) Unexpected there are “isolated” groups [Zn₄O₈]. Half of the Zn atoms exhibit the unusual coordination number 3 towards O^2?. The Madelung Part of Lattice Energy, MAPLE, and the Effective Coordination Number, ECoN, the latter by means of Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Über quaternäre Oxowolframate (VI) Na6Li2[W2O10] - ein Diwolframat

On Quaternary Oxotungstates (VI). Na₆Li₂[W₂O₁₀] — a Ditungstate For the first time, Na₆Li₂[W₂O₁₀] has been prepared by annealing mixtures of WO₃, Na₂O and Li₂O with W:Na:Li = 1:3:1 [closed Pt-tube in quartz-glass ampoule, 840°C, 60 d (single crystals)]. The colourless crystals are of squatted shape. The structure determination [1813/I₀(h kl), four-cycle diffractometer PW 1100 (Fa. Philips), ω-scan, AgK_α, R = 8.32%, absorption not considered] confirms the space group P1 with a = 784.66(11), b = 602.53(7) c, = 563.81(11) pm α = 106.784(14)°, β = 114.548(14)°, γ = 91.082(13)°, Z = 2, d_x = 4.92 g · cm^?3, d^pyk = 4.85 g · cm^?3. The structure may be described as a distorted derivative of the NaCl-type. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Neue Oxoterbate(IV) mit Lithium Rb2Li14[Tb3O14] und Li6Tb2O7

New Oxoterbates(IV) with Lithium: On Rb₂Li₁₄[Tb₃O₁₄] and Li₆Tb₂O₇ For the first time we prepared Rb₂Li₁₄[Tb₃O₁₄] as yellow single crystals from Li₈TbO₆ and Rb₂O (Tb:Rb = 1:2) [Ag-cylinder, 500°C, 30 d, then Au-tube, 700°C, 27 d]. The structure refinement [652 I₀ (h kl), four circle diffractometer Philips PW 1100, ω-scan, MoKα, R = 4.69%, R_w = 3.24%, absorption considered, Immm with a = 1 283.07(10), b = 790.87(7), c = 736.87(7)pm, Z = 2, d_x = 4.30 g · cm^?3] confirms that it is isotypic with K₂Li₁₄[Pb₃O₁₄]. Furthermore we got for the first time Li₆Tb₂O₇ as a bright yellow compound from Li₂O₂ and “Tb₄O₇*” [(Li:Tb = 3.4:1), Au-ube, 750°C, 13 d (powder), 850°C 22 d (single crystals)] and by thermal decomposition of Rb₂Li₁₄[Tb₃O₁₄] (Au-tube, 850°C, 25 d). Powder and single crystal data [1 327 I₀ (h kl), four circle diffractometer PW 1100, ω-scan, AgKα, R = 9.38%, R_w = 5.23%, absorption not considered, P2₁/a, a = 1 056.30(10), b = 613.50(4), c = 546.56(5) pm, β = 109.668(7)°, Z = 2, d_x = 4.67 g · cm^?3 d_pyc = 4.53 g · cm^?3] reveal a new type of structure that may be deduced by the NaCl-type of structure. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Neue Oxoplumbate(II) A2PbO2 (A = K,Rb, Cs) mit zweikernigen Gruppen [OPbO2PbO]

New Oxoplumbates(II) A₂PbO₂ (A = K, Rb, Cs), with Binuclear Groups [OPbO₂PbO] Unknown K₂PbO₂, Rb₂PbO₂ and Cs₂PbO₂ (yellowish powder, yellowish transparent single crystals, respectively) have been prepared, The compounds crystallize triclinic with a = 10.90₁ Å, b = 7.60₆ Å, c = 7.32₈ Å, α = 119.3₅°, β = 88.4₂°, γ =117,7₃°, (K₂PbO₂); a = 10.90₇ Å, b = 8.51₀ Å, c = 7.81₅ Å, α = 124.0₀°, β = 84.9₇°, γ = 120.6₈° (Rb₂PbO₂) and a = 11.64₄ Å, b = 8.90₅ Å, c = 8.04₀ Å, α = 123.3₂°, β = 85.7₀°, γ = 120.4₉° Z = 4, space group P1 -C/_i¹. For K₂PbO₂ we find R = 8.6₅% and R_w = 9.3₂% (2283 independent reflections). Parameters see text. There are isolated [Pb₂O₄]groups, which are connected in a complicated way by mutual K⁺ ions forming layers. The Madelung Part of the Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these by means of mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Rb2TiO3, ein neues Oxotitanat mit der Koordinationszahl 4

Rb₂TiO₃, a New Oxotitanate with Coordination Number 4 Rb₂TiO₃ cristallizes according to single crystal datas [544 Okl? 4kl, Mo? Kα] orthorhombic, a = 6.01₅, b = 11.93₆, c = 13.36₆ Å, Z = 8, space group D? Cmca, d_rö = 3.69, d_pyk = 3.65 g cm^?3; for occupied positions and atomic parameters see text. Surprisingly the coordination number of Ti to 0 turns out to be 4. The chains [TiO_1/1O_1/1O_2/2] are placed along [100]. The Madelung part of lattice energy (MAPLE) of Rb₂TiO₃ is calculated and discussed. In order to display the characteristics of the structure, further MAPLE-calculations have been carried out. K₂TiO₃ belongs to the Cs₂PbO₃-Family of structure with C.N. 5 of Ti to 0. Cs₂TiO₃ and Rb₂TiO₃ are not isotypic.     

Über gemischtvalente Oxoplumbate. Zur Kenntnis von Rb2Pb4O7 = Rb2PbPbO7

On Mixed-valent Oxoplumbates. On Rb₂Pb₄O₇ = Rb₂Pb Pb O₇ For the first time, Rb₂Pb₄O₇ has been prepared by annealing mixtures of Rb₂O₃ and PbO with Rb:Pb = 1:2 [Ag-cylinders, sealed under vacuum in Duran-glass ampoule, 450°C, 30 d (single crystals)]. The rubin red single crystals are of longish [001] shape. The structure determination [5162 symmetry independent hkl, four-circle-diffractometer CAD 4 (Fa. Enraf-Nonius), ω-2Θ—scan, AgKα, ψ-scan absorption correction, R = 7.54%, R_W = 7.71%] confirms the space group P1 with a = 1036.00(10), b = 733.72(8), c = 663.54(10) pm, α = 90.049(12)°, β = 99.236(12)°, γ = 101.641(12)°, Z = 2, d_rö = 7,58 g · cm^?3, d_pyk = 7,55 g · cm^?3. The structure is characterized by a layer-lattice. The coordination number is three for Pb²⁺, six for Pb⁴⁺. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Effective Ionic Radii, MEFIR, are calculated.     

Ein neues Cobaltat mit Inselstruktur: Li6[CoO4]

A New Cobaltate with Isolated Anion Structure: Li₆[CoO₄] For the first time transparent, blue single crystals of Li₆[CoO₄] have been prepared (Li₂O/Na₂O/?CoO”? (Li:Na:Co = 1.3:1.3:1), Co-tube, 580°C, 22 d). Corresponding to Li₆□CoO; it is an ordered variant of the Li₂O-type of structure: P4₂/nmc; a = 653.6(1) pm, c = 465.4(1) pm; Z = 2; d_x = 2.75 g cm^?3, d_pyk = 2.71 g cm^?3 (4-circle-diffractometer-data (PW 1100), AgKα; 230 from 936 I₀(hkl); R = 9.58%, R_W = 5.25%). Parameters see text. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. The magnetic properties are measured in the temperature range of 14–297 K.     

Das erste gemischtvalente Oxoplumbat mit „isolierten”︁ Baugruppen: KNa7[PbIVO4][PbIIO3]

The First Mixed-valent Oxoplumbate with Isolated Anions. On KNa₇[Pb^IVO₄][Pb^IIO₃] For the first time KNa₇Pb₂O₇ has been prepared by reaction of K and Na Oxides with ?PbO₂”? rsp. PbO_red [e. g.: KO_0.48:NaO_0.36:?PbO₂”? = 1:7:2 (Ag-cylinders, reduced Ar-pressure, sealed in supremax-glas ampoules, 600°C, 14 d): redorange single crystals of plated shape]. The structure determination [3269 I_o(hkl), four-circle diffractometer PW 1100 (Fa. Philips), ω-scan, MoKα, R = 9.52%, R_w = 7.67%, absorption not considered] proves the space group P2₁/c with a = 1758.48(10), b = 596.76(3), c = 1066.46(8) pm, β = 90.682(8)°, Z = 4, d_x = 4.311, d_pyk = 4.28 g/cm³. The structure is characterized by isolated [Pb^IVO₄] (symmetry nearly T_d) and [Pb^IIO₃] groups (symmetry nearly C_3v), the latter connected by cations to double-layers. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Oxide eines neuen Formeltyps: Zur Kenntnis von K3Ni2O4 und K3Pt2O4

Oxides of a New Type of Formula: On the Knowledge of K₃Ni₂O₄ and K₃Pt₂O₄ K₃Ni₃O₄, greyblack single crystals, obtained by heating K₂O and NaNiO₂ [K:Ni = 2:1, 500°C, 7d, Ag-cylinders], crystallizes orthorhombic with a = 6.04₄, b = 9.04₉, c = 10.56₇ Å, Z = 4, space group Cmcm (d_rö = 3.43, d_pyk = 3.32 g · cm^?3). Due to four cycle diffractometer data (374 hkl, MoKα, R = 8.6percnt;) a new type of structure is found with wavebands of [NiO_4/2] \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm 1} $\end{document} exhibits the C.N. 6, \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm 2} $\end{document} the C.N. 4. Effective Coordination Numbers, ECoN, calculated by means of Mean Fictive Ionic Radii, MEFIR, the Madelung Part of Lattice Energy, MAPLE and the magnetic properties are discussed. K₃Pt₂O₄, black single crystals with metallic lustre, obtained by heating KO_x (x = 1.55 or 1.88) and Pt (powder) [K:Pt = 4:1,1000°C, lh, 600°C, 2d, Pt-capsules] is isotypic to K₃Ni₂O₄ (four cycle diffractometer data: 458 hkl, MoKα, R = 12percnt;). Cellparameters are a = 6.15, b = 9.27, c = 11.51 Å (single crystal data), d_rö = 5.79 and d_pyk = 5.77 g · cm^?3.     

Quaternäre Monoborate der Alkalimetalle: Na4Li5[BO3]3

Quaternary Monoborates of Alkali Metals: Na₄Li₅[BO₃]₃ We prepared hitherto unknown Na₄Li₅[BO₃]₃ in the shape of monoclinic, colourless-transparent and prismatic single crystals [a = 1238.8(5) pm, b = 729.6(3) pm, c = 973.8(3) pm, β = 107,29(4)°, Z = 4, d_x = 2,397 g/cm³, d_pyk = 2,37 g/cm³]. The crystal structure was solved by four-circle-diffractometer [PW 1100, MoKα , R = 9,02%, R_w = 5,29%, 1221 I₀(hkl)]I₀(hkl)]. Na₄Li₅[BO₃]₃ is sensitive against atmospheric moisture; hydrolysis takes place within 60 minutes. Effective Coordination numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, and the Madelung Part of Lattice Energy, MAPLE, are calculated and discussed.     

Über Oxocadmate: Die Kristallstruktur von K2CdO2

On oxocadmates: The crystal structure of K₂CdO₂ According to single crystal data [438 hk0 — hk4; Mo — K_α] K₂CdO₂ crystallizes orthorhombic, space group No. 60, Pbcn — D, with a = 10.08₉, b = 6.18₆, c = 6.15₂ Å, Z = 4; d_rö = 3.85 g · cm^?3, d_pyk = 3.6₁ g · cm^?3 (for parameters see text). Though the space group is different from that of K₂ZnO₂, the similarities of the two crystal structures are unmistakable. The Madelung part of lattice energy is calculated and discussed.