Two new L-alanine compounds (alanine alaninium triiodide (1), s.g. P2 1 2 1 2 1 , a = 8.366(2) Å,... more Two new L-alanine compounds (alanine alaninium triiodide (1), s.g. P2 1 2 1 2 1 , a = 8.366(2) Å, b = 8.912(2) Å, c = 41.889(8) Å and alanine SrCl 2 3H 2 O (2), s.g. P2 1 , a = 8.540(2) Å, b = 7.167(1) Å, c = 8.769(2) Å, β = 95.02(3)°) have been prepared and characterised by X-ray single crystal analysis. The crystal structure of (1) features the presence of two independent molecules of alanine, alaninium and triiodide, respectively, in the asymmetric unit, with a very strong hydrogen bond between the carboxylate groups of alanine and alaninium. Compound (2) is composed of infinite zigzag chains of [SrO 7 Cl]-polyhedra, with alanine molecules and chloride ions in the interstices. By the study of the thermal behaviour of (1) via thermogravimetry and temperature resolved X-ray powder diffraction it was found that the compound is stable up to approx. 363 K and that the thermal expansion along c is only about 1/3 compared to a and b.
Acta Crystallographica Section E Structure Reports Online, 2007
The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodi... more The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodium titanium tetrasilicate dihydrate), Na4Ti2Si8O22. 4H2O, grown as small single crystals without the use of organics, has been refined from single-crystal X-ray diffraction ...
Neues Jahrbuch für Mineralogie - Monatshefte, 2002
ABSTRACT The crystal structures of bismutocolumbite, (Bi0.99Sb0.01)(Nb0.79Ta0.21)O4 (I) and stibi... more ABSTRACT The crystal structures of bismutocolumbite, (Bi0.99Sb0.01)(Nb0.79Ta0.21)O4 (I) and stibiocolumbite, Sb(Nb0.67Ta0.33)O4 (II) were established from X-ray single crystal diffraction; I, orthorhombic, space group Pnna, a = 5.668(1)Å, b = 11.725(2)Å, c = 4.971(1)Å, V = 330.4Å3, Z = 4, dcalc. = 7.726, dobs. = 7.17-7.56g/cm3, F(000) = 614, R = 0.025 for 820 unique reflections with I > 2(I); II, orthorhombic, space group Pna21a = 5.557(1)Å, b = 4.932(1)Å, c = 11.808(2)Å, V = 323.6Å3, Z = 4, dcalc. = 6.316, F(000) = 538, R = 0.023 for 1437 reflections with I > 2(I). In both structures (Nb,Ta) atoms have octahedral coordination. In I Bi-O distances within distorted octahedron range from 2.126 to 2.738Å; (Nb,Ta)-O distances are between 1.852-2.148 Å, in II Sb-O distances range from 2.008 to 2.619Å within distorted pseudotrigonal bypiramid; (Nb,Ta)-O distances are between 1.848 - 2.085Å. Both structures contain sheets of corner-linked (Nb,Ta)O6-octahedra separated by significantly distorted BiO6(SbO5)-polyhedra with four shorter distances opposite to the lone-pair electrons of Bi3+(Sb3+). The repulsive forces between lone-pair electrons and the O atoms lead to the distortion of (Nb,Ta)O6 octahedra in the stibiotantalite structure type. Two shortest bonds (Nb,Ta)-O(1) = 1.852Å in I as well as (Nb,Ta)-O(4) and -O(3) = 1.848 and 1.891Å, respectively, in II occur with ligands which are oriented in the direction of the lone-pair electrons of Bi3+(Sb3+) and which form the elongated bonds Bi-O(1) = 2.738Å in I and Sb-O(3) = 2.619Å and Sb-O(4) = 3.012Å in II. The structures of I and II with a close packing indices (CPI) of 54 and 55, respectively, can not be considered as atomic ones in contrast to some other ABO4 oxides with 6-fold coordination of cations, namely wolframite (Fe,Mn)[6]W[6]O4 (CPI = 68) and rutile-like CrVO4 (CPI = 74). The structural transitions (Pna21 to Pnna) in (Bi,Sb)(Nb,Ta)O4 series should be considered as a function of chemical composition, temperature and pressure.
ABSTRACT Chemical and structural variations of 11 minerals of the cancrinite group having an Al,S... more ABSTRACT Chemical and structural variations of 11 minerals of the cancrinite group having an Al,Si,O framework of the AB type are summarized and discussed. The total number of chemically studied samples is 360 (our data and literature data): cancrinite 192 and 35, vishnevite 21 and 13, cancrisilite 19 and 10, kyanoxalite and oxalate-rich intermediate members of the cancrinite-kyanoxalite series 12 and 0, davyne 10 and 23, depmeierite 2 and 0, balliranoite 1 and 0, hydroxycancrinite 0 and 1, quadridavyne 0 and 10, microsommite 0 and 8, and pitiglianoite 0 and 3. We provide original structural data for nine samples of distinct varieties of cancrinite and one sample of cancrisilite, as well as published structural data on the above-listed minerals. The major topics are the distribution and ratios of extra-framework components, cations (Na+, Ca2+, K+), anions (CO32-, SO42-, Cl-, C2O42-, PO43-) and H2O, with special emphasis on oxalate and phosphate anions. The idealized formula of cancrinite has been refined: Na7Ca[Al6Si6O24](CO3)(1.5)center dot 2H(2)O. The solid-solution series with coupled substitutions in the framework and extra-framework portions are discussed, as is the genetic aspect of crystal chemistry of cancrinite-group minerals with a AB-type framework.
Two new L-alanine compounds (alanine alaninium triiodide (1), s.g. P2 1 2 1 2 1 , a = 8.366(2) Å,... more Two new L-alanine compounds (alanine alaninium triiodide (1), s.g. P2 1 2 1 2 1 , a = 8.366(2) Å, b = 8.912(2) Å, c = 41.889(8) Å and alanine SrCl 2 3H 2 O (2), s.g. P2 1 , a = 8.540(2) Å, b = 7.167(1) Å, c = 8.769(2) Å, β = 95.02(3)°) have been prepared and characterised by X-ray single crystal analysis. The crystal structure of (1) features the presence of two independent molecules of alanine, alaninium and triiodide, respectively, in the asymmetric unit, with a very strong hydrogen bond between the carboxylate groups of alanine and alaninium. Compound (2) is composed of infinite zigzag chains of [SrO 7 Cl]-polyhedra, with alanine molecules and chloride ions in the interstices. By the study of the thermal behaviour of (1) via thermogravimetry and temperature resolved X-ray powder diffraction it was found that the compound is stable up to approx. 363 K and that the thermal expansion along c is only about 1/3 compared to a and b.
Acta Crystallographica Section E Structure Reports Online, 2007
The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodi... more The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodium titanium tetrasilicate dihydrate), Na4Ti2Si8O22. 4H2O, grown as small single crystals without the use of organics, has been refined from single-crystal X-ray diffraction ...
Neues Jahrbuch für Mineralogie - Monatshefte, 2002
ABSTRACT The crystal structures of bismutocolumbite, (Bi0.99Sb0.01)(Nb0.79Ta0.21)O4 (I) and stibi... more ABSTRACT The crystal structures of bismutocolumbite, (Bi0.99Sb0.01)(Nb0.79Ta0.21)O4 (I) and stibiocolumbite, Sb(Nb0.67Ta0.33)O4 (II) were established from X-ray single crystal diffraction; I, orthorhombic, space group Pnna, a = 5.668(1)Å, b = 11.725(2)Å, c = 4.971(1)Å, V = 330.4Å3, Z = 4, dcalc. = 7.726, dobs. = 7.17-7.56g/cm3, F(000) = 614, R = 0.025 for 820 unique reflections with I > 2(I); II, orthorhombic, space group Pna21a = 5.557(1)Å, b = 4.932(1)Å, c = 11.808(2)Å, V = 323.6Å3, Z = 4, dcalc. = 6.316, F(000) = 538, R = 0.023 for 1437 reflections with I > 2(I). In both structures (Nb,Ta) atoms have octahedral coordination. In I Bi-O distances within distorted octahedron range from 2.126 to 2.738Å; (Nb,Ta)-O distances are between 1.852-2.148 Å, in II Sb-O distances range from 2.008 to 2.619Å within distorted pseudotrigonal bypiramid; (Nb,Ta)-O distances are between 1.848 - 2.085Å. Both structures contain sheets of corner-linked (Nb,Ta)O6-octahedra separated by significantly distorted BiO6(SbO5)-polyhedra with four shorter distances opposite to the lone-pair electrons of Bi3+(Sb3+). The repulsive forces between lone-pair electrons and the O atoms lead to the distortion of (Nb,Ta)O6 octahedra in the stibiotantalite structure type. Two shortest bonds (Nb,Ta)-O(1) = 1.852Å in I as well as (Nb,Ta)-O(4) and -O(3) = 1.848 and 1.891Å, respectively, in II occur with ligands which are oriented in the direction of the lone-pair electrons of Bi3+(Sb3+) and which form the elongated bonds Bi-O(1) = 2.738Å in I and Sb-O(3) = 2.619Å and Sb-O(4) = 3.012Å in II. The structures of I and II with a close packing indices (CPI) of 54 and 55, respectively, can not be considered as atomic ones in contrast to some other ABO4 oxides with 6-fold coordination of cations, namely wolframite (Fe,Mn)[6]W[6]O4 (CPI = 68) and rutile-like CrVO4 (CPI = 74). The structural transitions (Pna21 to Pnna) in (Bi,Sb)(Nb,Ta)O4 series should be considered as a function of chemical composition, temperature and pressure.
ABSTRACT Chemical and structural variations of 11 minerals of the cancrinite group having an Al,S... more ABSTRACT Chemical and structural variations of 11 minerals of the cancrinite group having an Al,Si,O framework of the AB type are summarized and discussed. The total number of chemically studied samples is 360 (our data and literature data): cancrinite 192 and 35, vishnevite 21 and 13, cancrisilite 19 and 10, kyanoxalite and oxalate-rich intermediate members of the cancrinite-kyanoxalite series 12 and 0, davyne 10 and 23, depmeierite 2 and 0, balliranoite 1 and 0, hydroxycancrinite 0 and 1, quadridavyne 0 and 10, microsommite 0 and 8, and pitiglianoite 0 and 3. We provide original structural data for nine samples of distinct varieties of cancrinite and one sample of cancrisilite, as well as published structural data on the above-listed minerals. The major topics are the distribution and ratios of extra-framework components, cations (Na+, Ca2+, K+), anions (CO32-, SO42-, Cl-, C2O42-, PO43-) and H2O, with special emphasis on oxalate and phosphate anions. The idealized formula of cancrinite has been refined: Na7Ca[Al6Si6O24](CO3)(1.5)center dot 2H(2)O. The solid-solution series with coupled substitutions in the framework and extra-framework portions are discussed, as is the genetic aspect of crystal chemistry of cancrinite-group minerals with a AB-type framework.
Uploads
Papers by Ekkehart Tillmanns