Conveners
Disordered Materials, complex crystal structures and aperiodic crystals, diffuse scattering and 3D-PDF
- Martin v. Zimmermann (HASYLAB at DESY)
Disordered Materials, complex crystal structures and aperiodic crystals, diffuse scattering and 3D-PDF
- Sander van Smaalen (University of Bayreuth)
This contribution reports reversible, single-crystal-to-single-crystal phase transitions of commensurately modulated sodium saccharinate 1.875-hydrate [Na(sac)(15/8)H2O]. The phases were studied in the temperature range 298 to 20 K. They exhibit complex disordered states. An unusual reentrant disorder has been discovered upon cooling through a phase transition at 120 K. The...
Correlated disorder in crystalline materials gives rise to single crystal diffuse scattering. While the average structure determination via Bragg data analysis is considered a standard procedure, disorder analysis is thought of as a lengthy and complicated process. We present a mean field approximation to model single crystal diffuse scattering in molecular materials from a simple...
The group IV-VI chalcogenides have important thermoelectric applications. GeTe has emerged as a promis- ing non-toxic candidate, especially when the high-temperature cubic phase is suppressed to room tempera- ture. However, even the mechanism of phase transition is disputed, as is the presence of disorder. Here we combine ab initio MD with synchrotron X-ray and dynamic neutron pair...
R$_2$Ir$_3$Si$_5$ (R = Ho, Er, Lu) crystallize in the U$_2$Co$_3$Si$_5$ structure type at room temperature (orthorhombic space group Ibam) [1]. Upon cooling they undergo first-order charge-density-wave (CDW) phase transitions, as evidenced by anomalies with hysteresis in the temperature dependencies of the electrical resistivity ($\rho$), specific heat ($C_p$), magnetic susceptibility...
What is the complexity of a crystal structure? The definition of complexity is a challenging and similarly fascinating subject, touching different scientific disciplines such as economy, informatics, biology, math, and chemistry amongst others. Instead of defining complexity per sé, it is in practice easier to ask which system is more complex, showing that the challenge of defining...
Protection of amino acids is an essential aspect for peptide synthesis.[1] Recently, crystals of 4-biphenylcarboxy substituted L-serine, L-tyrosine, L-alanine, L-leucine and L-phenylalanine methyl esters have been demonstrated to possess diverse supramolecular assembly governed by C–H···π and π···π interactions between biphenyl fragments and intermolecular N–H···O interactions...
Single crystals often present disorder in their structure due to dopant substitution/intercalation or as an intrinsic instability of the compound. In many cases the disorder-to-order balance is responsible for key properties of the material. For example it can account for low thermal conductivity in PbTe or for the superconducting transition temperature in Sr2RuO4 where the highest Tc is...
Pentamers of transition metal octahedra and double semihelical chains of hydrogen bonds frame hureaulite-type oxyhydroxides (C2/c; a = 11.5 Å, b = 9.1 Å, c = 9.5 Å, beta = 96.4°) highly interesting for rich magnetic spin orders and polaron-dependent charge transport phenomena. Neutron powder diffraction data of its manganese end-member agree with that the magnetic lattice retains the (1a x 1b...
Ion- irradiation is an established technology to change properties of diamonds in a controlled way [1] and has been studied as a function of ion species, energy and fluence for many years [2-4]. However, little is known regarding surface effects for irradiations with high energy ions which penetrate deep into the diamond. Irradiation experiments were carried out on various synthetic diamond...
In the course of our studies on alkali trielides with mixed triel positions (Ga/In) [1] and (In/Tl), analysis of the binary phase diagrams Rb-Tl and Cs-Tl [2] show incongruent melting behaviour at the composition A Tl~$_{3}$ (A = Rb, Cs). A complete structural description of those phases has not been published to this day, even though Corbett and Dong [3] were able to determine the...
