scholarly journals The modulated structure of intermediate-valent CeCoGa

2016 ◽  
Vol 231 (3) ◽  
Author(s):  
Oliver Niehaus ◽  
Rolf-Dieter Hoffmann ◽  
Bernard Chevalier ◽  
Rainer Pöttgen
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Induction Furnace ◽  
Melting Furnace ◽  
Modulated Structure ◽  
X Ray ◽  
Arc Melting ◽  
Annealing Step ◽  
Different Temperatures ◽  
Intermediate Valent

AbstractCeCoGa was synthesized by melting of the elements in an arc-melting furnace as well as in a sealed niobium tube in an induction furnace. A further annealing step improves the purity and crystallinity of the samples significantly. Its structure was refined on the basis of single-crystal X-ray diffractometer data at different temperatures. Already at room temperature CeCoGa crystallizes in a superstructure of the HT-CeCoAl type. This superstructure can be described in the (3+1)D superspace group

Ternary Antimonides RE4T7Sb6 (RE=Gd–Lu; T =Ru, Rh) with Cubic U4Re7Si6-type Structure

2013 ◽  
Vol 68 (9) ◽  
pp. 971-978 ◽  
Author(s):  
Inga Schellenberg ◽  
Ute Ch. Rodewald ◽  
Christian Schwickert ◽  
Matthias Eul ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystal ◽  
Magnetic Moment ◽  
Induction Furnace ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Arc Melting ◽  
Intermediate Valent

The ternary antimonides RE4T7Sb6 (RE=Gd-Lu; T =Ru, Rh) have been synthesized from the elements by arc-melting and subsequent annealing in an induction furnace. The samples have been characterized by powder X-ray diffraction. Four structures were refined on the basis of single-crystal X-ray diffractometer data: U4Re7Si6 type, space group Im3m with a=862.9(2) pm, wR2=0.0296, 163 F2 values for Er4Ru7Sb6; a=864.1(1) pm, wR2=0.1423, 153 F2 values for Yb4Ru7Sb6; a=872.0(2) pm, wR2=0.0427, 172 F2 values for Tb4Rh7Sb6; and a=868.0(2) pm, wR2=0.0529, 154 F2 values for Er4Rh7Sb6, with 10 variables per refinement. The structures have T1@Sb6 octahedra and slightly distorted RE@T26Sb6 cuboctahedra as building units. The distorted cuboctahedra are condensed via all trapezoidal faces, and this network leaves octahedral voids for the T1 atoms. The ruthenium-based series of compounds was studied by temperature-dependent magnetic susceptibility measurements. Lu4Ru7Sb6 is Pauli-paramagnetic. The antimonides RE4Ru7Sb6 with RE=Dy, Ho, Er, and Tm show Curie-Weiss paramagnetism. Antiferromagnetic ordering occurs at 10.0(5), 5.1(5) and 4.0(5) K for Dy4Ru7Sb6, Ho4Ru7Sb6 and Er4Ru7Sb6, respectively, while Tm4Ru7Sb6 remains paramagnetic. Yb4Ru7Sb6 is an intermediate-valent compound with a reduced magnetic moment of 3.71(1) μB per Yb as compared to 4.54 μB for a free Yb3+ ion

Two superstructures of Ce3Rh4Ge4

2018 ◽  
Vol 233 (2) ◽  
pp. 81-95 ◽  
Author(s):  
Daniel Voßwinkel ◽  
Rolf-Dieter Hoffmann ◽  
Volodymyr Svitlyk ◽  
Wilfried Hermes ◽  
Magnus Greiwe ◽  
...  
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Melting Furnace ◽  
Type Structure ◽  
Temperature Dependent ◽  
X Ray ◽  
Arc Melting ◽  
Different Temperatures ◽  
Anisotropic Displacement Parameters ◽  
Structure Calculations

AbstractTwo different samples of Ce3Rh4Ge4were synthesized from different starting compositions by melting of the elements in an arc-melting furnace followed by annealing sequences in a sealed tantalum ampoule in a muffle furnace. The structures of two different stacking variants were refined on the basis of temperature dependent single-crystal X-ray diffractometer data. At high temperature Ce3Rh4Ge4adopts the U3Ni4Si4type structure with strongly enhanced anisotropic displacement parameters for the Rh1 atoms. For the two different crystals, additional reflections start to appear at different temperatures. The first crystal showed additional reflections already at room temperature (stacking variant I) and the second one showed additional reflections emerging below 270 K (stacking variant II). Stacking variant I could be described with the (3+1)D superspace groupI2/m(α0γ)00;α=1/2a*,γ=1/2c*; (Z=2), 1252F2values, 48 variables, wR=0.0306 for the main and wR=0.0527 for 440 1storder satellite reflections, similar to Pr3Rh4Ge4. For stacking variant II the (3+1)D superspace group isImmm(α00)00s;α=1/2a*; (Z=2). The structure could be refined with 1261F2values, 53 variables and residuals ofwR=0.0331 for the main reflections andwR=0.1755 (R1obs=0.0788) for the 1storder satellite reflections, [a=406.2(1),b=423.7(1) andc=2497.1(1) pm]. The commensurate description could be transformed to a three-dimensional (3D) supercell with space groupPnmaandZ=4:a=812.5(1),b=423.7(1),c=2497.1(2) pm, 1261F2values, 69 variables andwR=0.0525. The relation of the U3Ni4Si4type structure, the (3+1)D modulated and the 3D supercells are discussed on the basis of group-subgroup schemes. Ab initio electronic structure calculations are in line with the diffraction experiments, revealing the lowest total energy for thePnmaphase.

scholarly journals Intermediate-valent CeCoAl – a commensurate modulated structure with short Ce–Co distances

2015 ◽  
Vol 230 (9-10) ◽  
Author(s):  
Oliver Niehaus ◽  
Rolf-Dieter Hoffmann ◽  
Sophie Tencé ◽  
Bernard Chevalier ◽  
Rainer Pöttgen
Keyword(s):  
Single Phase ◽  
Induction Furnace ◽  
Structure Type ◽  
Furnace Annealing ◽  
Single Phase Sample ◽  
Modulated Structure ◽  
X Ray ◽  
Different Temperatures ◽  
Phase Sample ◽  
Intermediate Valent

AbstractCeCoAl was synthesized by melting of the elements in a sealed niobium tube in an induction furnace. Annealing of the sample gave access to a single phase sample. Its structure was refined on the basis of single-crystal X-ray diffractometer data at different temperatures. Above 271 K CeCoAl crystallizes in its own structure type in the space group

scholarly journals Analysis of LiKSO4 crystals in the temperature range from 573 to 943 K

2000 ◽  
Vol 56 (4) ◽  
pp. 607-617 ◽  
Author(s):  
Carlos Basílio Pinheiro ◽  
Marcos Assunção Pimenta ◽  
Gervais Chapuis ◽  
Nivaldo Lúcio Speziali
Keyword(s):  
Single Crystal ◽  
Phase Ii ◽  
Room Temperature ◽  
Structure Model ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Displacements ◽  
Disordered Models ◽  
Different Temperatures

The structural phases observed in LiKSO_4 crystals due to thermotropic transitions have been studied for more than a century. Nowadays many different phases are referenced, but some of the results are still controversial. Structural studies by single-crystal X-ray diffraction from room temperature to 803 K are presented here. Phase II (708 \lt T \lt 943 K) is extensively discussed on the basis of ordered and disordered models, using harmonic and anharmonic atomic displacements, and considering a twinned crystal composed of three orthorhombic domains. Analyses of the same phase at different temperatures determine the best structure model.

Condensed [PtIn3/3] and [PtIn6/6] Units as Structural Motifs in ScPtln, TbPtln, and HoPtln

2000 ◽  
Vol 55 (11) ◽  
pp. 1025-1030 ◽  
Author(s):  
Yaroslav V. Galadzhun ◽  
Vasyl' I. Zaremba ◽  
Holger Piotrowski ◽  
Peter Mayer ◽  
Rolf-Dieter Hoffmann ◽  
...  
Keyword(s):  
Single Crystal ◽  
Three Dimensional ◽  
Melting Furnace ◽  
Structural Motifs ◽  
Variable Parameters ◽  
Space Group ◽  
X Ray ◽  
Arc Melting ◽  
P Type ◽  
First Time

The ternary indides ScPtln, TbPtln, and HoPtln were synthesized by reaction of the elements in an arc-melting furnace and subsequent annealing for four weeks. ScPtln and HoPtln are reported here for the first time. The three indides crystallize with the hexagonal ZrNiAl structure, a ternary ordered version of the Fe2P type, space group P6̄2m. Single crystal X-ray data yielded a = 754.6(1), c = 348.31(8) pm, wR2 = 0.0390, 177 F2 values for ScPtln, a = 759.3(1), c = 387.6(1) pm, wR2 = 0.0576, 183 F2 values for TbPtln, and a = 758.13(1), c = 381.62(1) pm, wR2 = 0.0530, 239 F2 values for HoPtln with 14 variable parameters for each refinement. Striking structural motifs of these intermetallics are short Pt-In distances (270 - 286 pm) within the three-dimensional [Ptln] polyanions which are composed of Pt(2)In6 trigonal prisms and trigonal planar P t(l)In3 units. The platinum-indium substructure of ScPtln is discussed in comparison with the various platinum-indium networks in the structures of Ptln2, Pt3In7, SrPtln, Sr2Pt3ln4, SrPtIn2, LaPtIn3, and PtIn7Fi3.

Synthesis and Structure of YbIrIn5

2003 ◽  
Vol 58 (8) ◽  
pp. 805-808 ◽  
Author(s):  
Vasyl’ I. Zaremba ◽  
Ute Ch. Rodewald ◽  
Rainer Pöttgen
Keyword(s):  
Single Crystal ◽  
Cell Volume ◽  
Room Temperature ◽  
Variable Parameters ◽  
X Ray ◽  
Intermediate Valent

The new ternary indium-rich compound YbIrIn5 was synthesized from the elements via an indium flux technique. A mixture with the starting composition 1:1:7 was heated at 1300 K in a tantalum tube for 6 h and cooled to room temperature at a rate of 5 K/h. The structure was refined from X-ray single crystal diffractometer data: HoCoGa5 type, P4/mmm, a = 461.96(7), c = 740.21(15) pm, wR2 = 0.0616, 222 F2 values, and 12 variable parameters. The iridium atoms have eight indium neighbors in square prismatic coordination at Ir-In distances of 274 pm. The square prisms are condensed via common edges forming layers which are separated by the ytterbium and further indium atoms. Ytterbium has a cuboctahedral indium coordination. The cell volume is suggestive for divalent or intermediate-valent ytterbium.

Different Structural Models of YB2C2 and GdB2C2 on the Basis of Single-Crystal X-Ray Data

2014 ◽  
Vol 69 (3) ◽  
pp. 289-293 ◽  
Author(s):  
Olaf Reckeweg ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structural Model ◽  
Induction Furnace ◽  
Unit Cell ◽  
Nominal Composition ◽  
X Ray ◽  
Arc Melting ◽  
Tetragonal Unit Cell ◽  
Ray Methods

Samples of YB2C2 and GdB2C2 were synthesized by arc-melting and subsequent annealing of the products. Single crystals of the title compounds were examined with single-crystal X-ray methods. Five different tetragonal unit cell settings from the literature (obtained on the basis of symmetry considerations) were used for the refinement of the crystal structure of YB2C2, but a converging refinement was only achieved for the structural model in the space group P4=mbm (no. 127, Z = 2) with a = 533:27(3) and c = 354:58(3) pm, without obvious inconsistencies. Nevertheless, the results for the five different unit cell settings are compared and discussed. A refinement of the crystal structure of the isotypic compound GdB2C2 was also performed with the lattice parameters a = 537:46(6) and c = 364:98(11) pm. Neither EuB2C2 nor YbB2C2 were obtained by melting coldpressed pellets with the nominal composition RE1.5B2C2 in an arc-furnace or an induction furnace, or by just heating the pellets in sealed Ta ampoules

On the Silicides EuIr2Si2 and Lu5Si3

2004 ◽  
Vol 59 (9) ◽  
pp. 969-974 ◽  
Author(s):  
Ute Ch. Rodewald ◽  
Birgit Heying ◽  
Dirk Johrendt ◽  
Rainer Pöttgen
Keyword(s):  
Single Crystal ◽  
Chemical Bonding ◽  
Induction Furnace ◽  
Three Dimensional ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Arc Melting ◽  
Sample Chamber ◽  
Trigonal Prismatic Coordination ◽  
Trigonal Prismatic

EuIr2Si2 was synthesized from the elements in a sealed tantalum tube in a water-cooled sample chamber of an induction furnace. Lu5Si3 was obtained by arc-melting of the elements. Both silicides were investigated by X-ray powder and single crystal diffraction: BaAl4 type, I4/mmm, a = 407.4(1), c = 1010.8(7) pm, wR2 = 0.0492, 134 F2 values, 9 variables for EuIr2Si2 and Mn5Si3 type, P63/mcm, a = 820.0(1), c = 614.2(1) pm, wR2 = 0.0511, 311 F2 values and 12 variables for Lu5Si3. The iridium and silicon atoms in EuIr2Si2 build up a three-dimensional [Ir2Si2] network with Ir-Si and Si-Si interactions. The europium atoms fill cages within the network. The metal-rich silicide Lu5Si3 contains columns of face-sharing, empty Lu6 octahedra and isolated silicon atoms in a distorted tri-capped trigonal prismatic coordination. Chemical bonding in these silicides is briefly discussed.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

Sign in / Sign up

Export Citation Format

Share Document