Sander van Smaalen

University of Bayreuth, Bayreuth, Bavaria, Germany

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Publications (310)647.65 Total impact

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    ABSTRACT: YCa4O(BO3)3 (YCOB) crystals co-doped with 3at% Er3+ and 20at% Yb3+ were successfully grown by the Czochralski method. X-ray powder diffraction (XRPD) results show that the as-grown Er:Yb:YCOB crystal belongs to the monoclinic system with space group Cm. And the lattice parameters are aCombining double low line8.076(8)Å, bCombining double low line16.023(7)Å, cCombining double low line3.528(4)Å and βCombining double low line101.15(4)°. Crystal defects were revealed by chemical etching experiments. The density of etch pits, attributed to dislocations and observed on (010) planes, was found to be not uniform along the crystal diameter. The detailed polarized absorption spectra were measured. The polarized absorption cross sections at 977nm are 1.01×10g'20, 1.22×10g'20 and 1.05×10g'20cm2 for E//X, E//Y and E//Z, respectively. And the polarized absorption cross sections at 1538nm is about 1.86×10g'20cm2 for both E//X and E//Z, but for E//Y the result is 1.03×10g'20cm2, which is much smaller. The relationship between the crystal structure and absorption spectra was discussed.
    No preview · Article · Jan 2016
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    ABSTRACT: A unique combination of useful properties in boron-carbide, such as extreme hardness, excellent fracture toughness, a low density, a high melting point, thermoelectricity, semi-conducting behavior, catalytic activity and a remarkably good chemical stability, makes it an ideal material for a wide range of technological applications. Explaining these properties in terms of chemical bonding has remained a major challenge in boron chemistry. Here we report the synthesis of fully ordered, stoichiometric boron-carbide B13C2 by high-pressure-high-temperature techniques. Our experimental electron-density study using high-resolution single-crystal synchrotron X-ray diffraction data conclusively demonstrates that disorder and defects are not intrinsic to boron carbide, contrary to what was hitherto supposed. A detailed analysis of the electron density distribution reveals charge transfer between structural units in B13C2 and a new type of electron-deficient bond with formally unpaired electrons on the C-B-C group in B13C2. Unprecedented bonding features contribute to the fundamental chemistry and materials science of boron compounds that is of great interest for understanding structure-property relationships and development of novel functional materials.
    Preview · Article · Jan 2016 · Scientific Reports
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    Preview · Conference Paper · Aug 2015
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    Full-text · Article · Aug 2015 · Acta Crystallographica Section A: Foundations and Advances
  • Bing Teng · Weijin Kong · Ke Feng · Fei You · Lifeng Cao · Degao Zhong · Lun Hao · Qing Sun · Sander van Smaalen · Wenhui Gong
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    ABSTRACT: A new organic crystal of 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium benzene sulfonate (DASBS) was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST) with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBS center dot H2O was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232 degrees C.
    No preview · Article · Jun 2015 · Frontiers of Materials Science
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    ABSTRACT: The high-pressure behavior of layered CrOCl is shown to be governed by non-bonded interactions between chlorine atoms in relation to a rigid framework composed of Cr and O atoms. The competition between optimizing intra- and interlayer Cl-Cl distances and the general trend towards denser packing defines a novel mechanism for high-pressure phase transitions of inorganic materials. CrOCl possesses an incommensurate phase for 16-51 GPa. Single-crystal x-ray diffraction in a diamond anvil cell provides an accurate description of the evolution of the incommensurate wave with pressure. It thus demonstrates a continuous increase of the amplitude up to 30 GPa, followed by a decrease of the wavelength until a lock-in transition occurs at 51 GPa.
    Full-text · Article · May 2015 · Scientific Reports
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    ABSTRACT: The co-crystal of phenazine (Phz) and chloranilic acid (H2ca) becomes ferroelectric upon cooling through the loss of inversion symmetry. Further cooling results in the development of an incommensurate ferroelectric phase, followed by a lock-in transition towards a twofold superstructure. Here we present the incommensurately modulated crystal structure of Phz-H2ca at T = 139 K with a symmetry given by the superspace group P21(½ σ2 ½)0 and σ2 = 0.5139. The modulation mainly affects the positions of the protons within half of the intermolecular hydrogen bonds that are responsible for the spontaneous polarization in all three low-temperature phases. Evidence for proton transfer in part of the hydrogen bonds is obtained from the correlated dependence on the phase of the modulation of the lengths of bonds involved in resonance stabilization of the acidic anion, and much smaller variations of bond lengths of atoms not involved in the resonance mechanism. Incommensurability is explained as competition between proton transfer favored for single hydrogen bonds on the basis of pK a values and avoiding unfavorable Coulomb repulsion within the lattice of the resulting ionic molecules.
    Full-text · Article · Mar 2015 · Acta Crystallographica Section B
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    ABSTRACT: Several fcc- and hcp-structured Ir–Os alloys were prepared from single-source precursors in hydrogen atmosphere at 873 K. Their atomic volumes measured at ambient conditions using powder X-ray diffraction follow nearly linear dependence as a function of composition. Alloys have been studied up to 30 GPa at room temperature by means of synchrotron-based X-ray powder diffraction in diamond anvil cells. Their bulk moduli increase with increasing osmium content and show a deviation from linearity. Bulk modulus of hcp-Ir0.20Os0.80 is identical to that of pure Os (411 GPa) within experimental errors. Peculiarities on fcc-Ir0.80Os0.20 compressibility curve indicate possible changes of its electronic properties at ∼20 GPa.
    Full-text · Article · Feb 2015 · Journal of Alloys and Compounds
  • Sk Imran Ali · Swastik Mondal · Sander van Smaalen
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    ABSTRACT: Single crystals of CuxTa1+ySe2 were grown by chemical vapor transport. Single crystals of different compositions were obtained at slightly different reaction conditions from mixtures of the reactants of the same nominal composition. It is suggested that different diameters of the ampoules imply different contributions of convection and diffusion to the mass transport, and thus are responsible for different ratios of the amount of Cu, Ta, and Se transported. 2H-Cu0.52TaSe2 (x = 0.52, y = 0) is formed in the narrower ampoule (diameter 15 mm). The crystal structure is based on the MoS2 type of stacking of TaSe2 layers. Partial ordering of Cu over the tetrahedral sites is responsible for a 2a0 × 2b0 × c0 superstructure with hexagonal Pm2 symmetry [a0 = 3.468 (1) Å, c0 = 13.568 (3) Å]. 2H-Cu0.16Ta1.08Se2 (x = 0.16, y = 0.08) is formed in the wider ampoule (diameter 18 mm). It possesses a NbS2-type of stacking. A superstructure is not formed, but the presence of Cu and intercalated Ta in alternating van der Waals gaps is responsible for the reduction of symmetry from P63/mmc to Pm1 [a0 = 3.439 (2) Å, c0 = 12.870 (2) Å]. Single crystals are formed towards the hotter side of the ampoules up to a temperature of 1168 K in both reactions.
    No preview · Article · Feb 2015 · Zeitschrift für anorganische und allgemeine Chemie
  • Sander van Smaalen · Hans Boysen

    No preview · Article · Jan 2015
  • Mohammad Shaz · Rohit Shahi · Thakur Yadav · Onkar Srivasatava · Sander van Smaalen
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    ABSTRACT: The present study deals with the microstructural changes with respect to the processing parameter (quenching rate) and their correlation with hydrogen storage characteristics of Ti45Zr38Ni17 quasicrystalline alloys. The ribbons of the alloy have been synthesized at different quenching rates obtained through different wheel speeds (35, 40, 45 and 50 m/s) and investigated for their hydrogen storage characteristics. The lower cooling rate obtained through low wheel speed (35 m/s) produces, i-phase grains whose size ranges from 300- 350 nm, whereas higher cooling rates obtained through high wheel speed (45 and 50 m/s) promote the formation of grains with size ranges from 100-150 nm in Ti45Zr38Ni17 ribbons. It has been found that the ribbons synthesized at 35 m/s absorbed ∼2.0 wt%, whereas ribbons synthesized at 50 m/s absorbed ∼2.84 wt. % of hydrogen. Thus the hydrogen storage capacity of ribbon increases for the ribbons produced at higher quenching rate. One of the salient features of the present study is that the improvement of hydrogen storage capacity obtained through higher quenching rates (∼45 to 50 m/s wheel speed) leading to the formation of lower grain size.
    No preview · Article · Aug 2014 · Acta Crystallographica Section A: Foundations and Advances
  • Andreas Schönleber · Somnath Dey · Sander van Smaalen · Finn Larsen
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    ABSTRACT: The organic compound Λ-Co(sepulchrate) trinitrate, [C(12)H(18)N(8)Co](3+) 3[NO(3)](-), exhibits at room temperature a disordered structure in symmetry P6(3)22 [1,2]. The Co(sepulchrate) cation and two of the nitrate anions, all centred on three fold rotation axes, are linked via dense N--H...O hydrogen bond networks, the third nitrate anion, centred on the intersection of the two fold rotation axes, shows orientational disorder (see Figure). Three phase transitions have been observed upon cooling by means of light microscopy and spectroscopic measurements [1] and by single crystal neutron diffraction [3] at T(1) = 133 K, T(2) = 106 K and T(3) = 98 K. These phase transitions are interpreted as ordering of the disordered nitrate anions [1] and as reduction of symmetry from hexagonal to orthorhombic associated with twinning. The appearance of satellite reflections in the diffraction pattern at T(1) = 133 K indicates a modulated structure; as the positions of those satellite reflections are temperature dependent [3], the modulation is incommensurate. By single crystal X-ray diffraction at beam lines D3 and F1 of Hasylab (DESY, Hamburg) at different low temperatures we found that all observed peaks are indexable in an hexagonal setting and two q-vectors q(1)=(sigma,sigma,0) and q(2)=(-2sigma,sigma,0) with sigma = 0.0882. This setting is compatible with a three-fold orthorhombic twinning and one q-vector q(orth)=(2sigma,0,0) for each of the three twin domains, which allows to reduce the symmetry. Structure refinement of all three low temperature phases allows to set them into relation to each other.
    No preview · Conference Paper · Aug 2014
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    ABSTRACT: The compound TiOCl is a quasi-1-dimensional (1D) quantum magnet (Seidel et al., 2003). Upon cooling, TiOCl undergoes a phase transition at Tc2 = 90 K towards a state with incommensurate magnetic order, followed by a second phase transition at Tc1 = 67 K towards a spin-Peierls state (Seidel et al., 2003; Shaz et al., 2005; van Smaalen et al., 2005). Both low-temperature phases involve structural distortions that have been characterized by x-ray diffraction. The absence of any phase transitions has been reported for scandium-doped TiOCl with doping levels 0.01 < x < 0.1 for ScxTi1-xOCl (Glancy et al., 2008, 2010; Zhang et al., 2010; Aczel et al., 2011). We have synthesized ScxTi1-xOCl for x = 0.005. Based on temperature-dependent x-ray diffraction experiments and specific-hear measurements, we have found that the x = 0.005 compound transforms into incommensurate and spin-Peierls-like phases on cooling. Despite apparent large correlation lengths, these phases lack long-range order. A sluggish transformation is thus found between states of ScxTi1-xOCl that support different kinds of fluctuations.
    No preview · Conference Paper · Aug 2014
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    Christian Hübschle · Sander van Smaalen
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    ABSTRACT: The program suite BayMEM consists of the programs PRIOR, BayMEM and EDMA. It is intended to apply the Maximum Entropy Method (MEM) to ordinary and modulated structures[1]. The PRIOR program is intended to calculate the prior density for the MEM calculation, but it has been recently shown that it can be used to calculate the dynamic charge density from multipolar refinements[2] as well. As a new functionality it is now also possible to calculate the electrostatic potential from the dynamic deformation density by the method described by Steward and Spackman[3]. We will present a new MapConverter program which allows to convert electron density stored in different file formats into an other. It is also possible to rearrange and cut the density in such a way, that it is possible, to have clear view of one molecule, not obscured by its symmetry mates, in a molecular viewer like MoleCoolQt for example.
    Full-text · Article · Aug 2014 · Acta Crystallographica Section A: Foundations and Advances
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    ABSTRACT: The co-crystal of phenazine (Phz) and chloroanilic acid (H2ca) is ferroelectric below the temperature T[I](c) = 253 K (FE-I phase). Upon cooling, two more phase transitions involve a further reduction of symmetry, until Phz-H2ca is triclinic in the second ferroelectric phase (FE-II phase) stable below T[II](c) = 137 K. Ferroelectricity in all low-temperature phases is believed to be related to partial proton transfer within the hydrogen bonds between the molecules Phz and H2ca. Here we present the crystal structure of the FE-II phase at T = 100 K. Experimental positions of hydrogen atoms indicate that ferroelectricity is mainly governed by half of the hydrogen-bonded chains, whereby proton transfer is observed within one of the two hydrogen bonds in which each molecule participates. A simple point charge model quantitatively reproduces the polarisation of this material. However, a possible contribution to the polarisation is proposed of the O-H...N hydrogen bonds of the second half of the mixed chains, which show elongated O-H bonds similar to those in the FE-I phase. The twofold superstructure with P1 symmetry was successfully solved as commensurately modulated structure employing the monoclinic superspace group P 2(1) (1/2 , s2 , 1/2) 0. The latter shows that the distortions at low temperatures follow a single normal mode of the space group P 2(1) of the FE-I phase, and it thus explains that the direction of the polarisation remains close to the monoclinic axis, despite the lowering towards triclinic symmetry.
    Full-text · Article · Aug 2014 · Journal of Chemical Crystallography
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    ABSTRACT: At low temperatures the organic salt adamantan-1-ammonium 4-fluorobenzoate, C10H18N(+)·C7H4FO2(-), possesses an incommensurately modulated crystal structure. The effect of the modulation on the atomic arrangement and intermolecular interactions is studied by analysing single-crystal X-ray diffraction data within the (3 + 1)-dimensional superspace approach and superspace group P21/n(α0γ)00. The modulation strongly affects the position of the atoms as well as their atomic displacement parameters. Nevertheless, the molecular cations and anions are built by rigid moieties, which vary their orientation with respect to each other as a function of the phase of the modulation t. Cations and anions are connected into slabs by dense N-H...O and C-H...F hydrogen-bonded networks, which are characterized by being rather rigid and which show only a little variation as a function of the phase of the modulation t.
    Full-text · Article · Aug 2014 · Acta Crystallographica Section B: Structural Science
  • C. Botta · V. Kahlenberg · C. Hejny · D. M. Toebbens · M. Bykov · S. van Smaalen
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    ABSTRACT: Polycrystalline material of a sulfate apatite with chemical composition Na6Ca4(SO4)6F2 or (Na2Ca4)Na4(SO4)6F2 has been synthesized by solid state reactions. Basic crystallographic data are as follows: hexagonal symmetry, a = 9.3976(1) Å, c = 6.8956(1) Å, V = 527.39(1) Å3, Z = 1, space group P63/m. For structural investigations the Rietveld method was employed. Thermal expansion has been studied between 25 and 600 °C. High temperature (HT) powder diffraction data as well as thermal analysis indicate that the apatite-type compound undergoes a reconstructive phase transition in the range between 610 and 630 °C. Single-crystals of the HT-polymorph were directly grown from the melt. Structural investigations based on single-crystal diffraction data of the quenched crystals performed at −100 °C showed orthorhombic symmetry (space group Pna21) with a = 12.7560(8) Å, b = 8.6930(4) Å, c = 9.8980(5) Å, V = 1097.57(10) Å3 and Z = 2. Unit cell parameters for a quenched polycrystalline sample of the HT-form obtained at ambient conditions from a LeBail-fit are as follows: a = 12.7875(1) Å, b = 8.7255(1) Å, c = 9.9261(1) Å, V = 1107.53(2) Å3. The lattice parameters of both modifications are related by the following approximate relationships: a HT ≈ 2c RT, b HT ≈ -(½a RT + b RT), c HT ≈ a RT. The HT-modification is isotypic with the corresponding potassium compound K6Ca4(SO4)6F2. The pronounced disorder of the sulphate group even at low temperatures has been studied by maximum entropy calculations. Despite the first-order character of the transformation clusters of sulfate groups surrounding the fluorine anions can be identified in both polymorphs. Each of the three next neighbor SO4-tetrahedra within a cluster is in turn surrounded by 8–9 M-cations (M: Na,Ca) defining cage-like units. However, in the apatite structure the corresponding three tricapped trigonal prisms are symmetry equivalent. Furthermore, the central fluorine atom of each cluster is coordinated by three next M-neighbors (FM3-triangles), whereas in the HT-polymorph a four-fold coordination is observed (FM4-tetrahedra).
    No preview · Article · Aug 2014 · Mineralogy and Petrology
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    Full-text · Dataset · Aug 2014
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    ABSTRACT: Single crystals of ScxTi1−xOCl (x = 0.005) have been grown by the vapor phase transport technique. Specific heat measurements prove the absence of phase transitions for 4–200 K. Instead, an excess entropy is observed over a range of temperatures that encompasses the incommensurate phase transition at 90 K and the spin-Peierls transition at 67 K of pure TiOCl. Temperature-dependent x-ray diffraction on ScxTi1−xOCl gives broadened diffraction maxima at incommensurate positions between Tc1 = 61.5 (3) and ∼90 K, and at commensurate positions below 61.5 K. These results are interpreted as due to the presence of an incommensurate phase without long-range order at intermediate temperatures, and of a highly disturbed commensurate phase without long-range order at low temperatures. The commensurate phase is attributed to a fluctuating spin-Peierls state on an orthorhombic lattice. The monoclinic symmetry and local structure of the fluctuations are equal to the symmetry and structure of the ordered spin-Peierls state of TiOCl. A novel feature of ScxTi1−xOCl (x = 0.005) is a transformation from one fluctuating phase (the incommensurate phase at intermediate temperatures) to another fluctuating phase (the spin-Peierls-like phase). This transformation is not a phase transition occurring at a critical temperature, but it proceeds gradually over a temperature range of ∼10 K wide. The destruction of long-range order requires much lower levels of doping in TiOCl than in other low-dimensional electronic crystals, like the canonical spin-Peierls compound CuGeO3. An explanation for the higher sensitivity to doping has not been found, but it is noticed that it may be the result of an increased two-dimensional character of the doped magnetic system. The observed fluctuating states with long correlation lengths are reminiscent of Kosterlitz–Thouless-type phases in two-dimensional systems.
    No preview · Article · Jul 2014 · Physical Review B
  • Sk Imran Ali · Sander van Smaalen
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    ABSTRACT: Single crystals of Cu3TaSe4 are obtained from a precursor that is produced by chemical vapor reaction of Cu, Ta, and Se in a molar ratio of 0.21:1.15:2 (quartz ampoule in two-zone furnace, 1.
    No preview · Article · Jun 2014 · ChemInform

Publication Stats

3k Citations
647.65 Total Impact Points

Institutions

  • 1996-2015
    • University of Bayreuth
      • • Bavarian Research Institute of Experimental Geochemistry and Geophysics
      • • Institute of Physics
      • • Chair of Crystallography
      Bayreuth, Bavaria, Germany
  • 1987-2007
    • University at Buffalo, The State University of New York
      • Department of Chemistry
      Buffalo, New York, United States
  • 2002
    • International Union of Toxicology
      Reston, Virginia, United States
  • 1985-2000
    • University of Groningen
      • Materials Science Group
      Groningen, Groningen, Netherlands
  • 1990
    • Institut de Physique et Chimie des Matériaux de Strasbourg
      Strasburg, Alsace, France
  • 1986
    • University of Antwerp
      Antwerpen, Flanders, Belgium