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Acta Cryst. (2014). A70, C103
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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.

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Acta Cryst. (2014). A70, C169
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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)=(σ,σ,0) and q(2)=(-2σ,σ,0) with σ ≍ 0.0882. This setting is compatible with a three-fold orthorhombic twinning and one q-vector q(orth)=(2σ,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.

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Acta Cryst. (2014). A70, C183
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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.

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Acta Cryst. (2014). A70, C263
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The complex interplay between spin, charge, orbital, and lattice degrees of freedom has made low-dimensional quantum spin magnets with strong antiferromagnetic (AF) spin-exchange coupling prime candidates for studying unusual magnetic phenomena. A progressive spin-lattice dimerization in one-dimensional AF Heisenberg chains, which occurs below a critical temperature and induces a singlet ground state with a magnetic gap, is commonly referred to as spin-Peierls (SP) transition. Recently, the compounds TiOX (X = Cl, Br) and TiPO4 have been intensively investigated due to their unconventional behavior [1,2]. Unlike standard SP systems, TiOX and TiPO4 undergo a sequence of normal-incommensurate-commensurate phase transitions on cooling at remarkably high transition temperatures. The transition temperatures are related to the direct exchange interactions between Ti ions, which increases strongly with decreasing the distance between the Ti ions, and therefore is very sensitive to the applied hydrostatic pressure. We have performed pressure-dependent single-crystal X-ray diffraction of TiPO4 using synchrotron radiation. TiPO4 undergoes a pressure-induced pahse transiton towards an incommensurate phase already below 10 GPa. This transformation is followed by the lock-in phase transition to the dimerized SP phase. Both structures are analogous to those at low temperatures, but reveal significantly larger modulation amplitudes. In this contribution we will present the detailed discussion of the high-pressure structures of TiPO4 and their behavior on compression. Furthermore, similarities and differences of high-pressure phase diagrams of TiOCl and TiPO4 and discrepancies between predicted and observed structures will be considered.

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Acta Cryst. (2014). A70, C1772
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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.
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