Search results for "metals"
showing 10 items of 2013 documents
Energetics of conformational conversion between 1,1,2-trichloroethane polymorphs
2008
Pressure-induced transformations between gauche-, gauche+ and transoid conformations have been evidenced by X-ray single-crystal diffraction for 1,1,2-trichloroethane, and the energies of intermolecular interactions, conformational conversion, and the latent heat have been determined.
Crystal structure analysis of a star-shaped triazine compound: a combination of single-crystal three-dimensional electron diffraction and powder X-ra…
2017
The solid-state structure of star-shaped 2,4,6-tris{(E)-2-[4-(dimethylamino)-phenyl]ethenyl}-1,3,5-triazine is determined from a powder sample by exploiting the respective strengths of single-crystal three-dimensional electron diffraction and powder X-ray diffraction data. The unit-cell parameters were determined from single crystal electron diffraction data. Using this information, the powder X-ray diffraction data were indexed, and the crystal structure was determined from the powder diffraction profile. The compound crystallizes in a noncentrosymmetric space group,P212121. The molecular conformation in the crystal structure was used to calculate the molecular dipole moment of 3.22 Debye,…
Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K
2017
A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The si…
Structural and electrical study of the topological insulator SnBi2Te4 at high pressures
2016
We report high-pressure X-ray diffraction and electrical measurements of the topological insulator SnBi2Te4 at room temperature. The pressure dependence of the structural properties of the most stable phase of SnBi2Te4 at ambient conditions (trigonal phase) have been experimentally determined and compared with results of our ab initio calculations. Furthermore, a comparison of SnBi2Te4 with the parent compound Bi2Te3 shows that the central TeSnTe trilayer, which substitutes the Te layer at the center of the TeBiTeBiTe layers of Bi2Te3, plays a minor role in the compression of SnBi2Te4. Similar to Bi2Te3, our resistance measurements and electronic band structure simulations in SnBi2Te4 at hi…
Thermal equation of state of ruthenium characterized by resistively heated diamond anvil cell
2019
AbstractThe high-pressure and high-temperature structural and chemical stability of ruthenium has been investigated via synchrotron X-ray diffraction using a resistively heated diamond anvil cell. In the present experiment, ruthenium remains stable in the hcp phase up to 150 GPa and 960 K. The thermal equation of state has been determined based upon the data collected following four different isotherms. A quasi-hydrostatic equation of state at ambient temperature has also been characterized up to 150 GPa. The measured equation of state and structural parameters have been compared to the results of ab initio simulations performed with several exchange-correlation functionals. The agreement b…
Phase diagram of calcium at high pressure and high temperature
2018
Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murn…
Pressure-induced amorphization of the Y3Ga5O12 garnet studied to 1 Mbar
2020
We use micro-beam synchrotron x-ray diffraction to study the pressure-induced amorphization of nano-sized and single crystals of Y3Ga5O12 up to pressures exceeding 1 Mbar in static compression. The abrupt pressure-induced amorphization found for both 56 nm and bulk micrometric crystals at around 76 GPa independently of the pressure transmitting medium employed demonstrates its intrinsic nature, previously predicted at 79 GPa by ab initio calculations. The single crystal structural solution at 50 GPa shows that the contraction of the unit-cell, mostly accommodated by the compressible YO8 dodecahedra, gives rise to a regularization and tilting increase of the GaO6 polyhedra with the Y?O-Ga an…
Enhanced chemosensing of ammonia based on the novel molecular semiconductor-doped insulator (MSDI) heterojunctions
2011
Abstract A series of new molecular semiconductor-doped insulator (MSDI) heterojunctions as conductimetric transducers to NH3 sensing were fabricated based on a novel semiconducting molecular material, an amphiphilic tris(phthalocyaninato) rare earth triple-decker complex, Eu2[Pc(15C5)4]2[Pc(OC10H21)8], quasi-Langmuir–Shafer (QLS) film, as a top-layer, and vacuum-deposited and cast film of CuPc as well as copper tetra-tert-butyl phthalocyanine (CuTTBPc) QLS film as a sub-layer, named as MSDIs 1, 2 and 3, respectively. MSDIs 1–3 and respective sub-layers prepared from three different methods were characterized by X-ray diffraction, electronic absorption spectra and current–voltage (I–V) measu…
Epitaxial growth and thermoelectric properties of TiNiSn and Zr0.5Hf0.5NiSn thin films
2011
Abstract Due to their exceptional thermoelectric properties Half-Heusler alloys like MNiSn (M = Ti,Zr,Hf) have moved into focus. The growth of single crystalline thin film TiNiSn and Zr 0.5 Hf 0.5 NiSn by dc magnetron sputtering is reported. Seebeck and resistivity measurements were performed and their dependence on epitaxial quality is shown. Seebeck coefficient, specific resistivity and power factor for Zr 0.5 Hf 0.5 NiSn at room temperature were measured to be 63 μV K − 1 , 14.1 μΩ m and 0.28 mW K − 2 m − 1 , respectively. Multilayers of TiNiSn and Zr 0.5 Hf 0.5 NiSn are promising candidates to increase the thermoelectric figure-of-merit by decreasing thermal conductivity perpendicular …
GdBO3 and YBO3 crystals under compression
2021
High-pressure X-ray diffraction studies on nanocrystals of the GdBO3 and YBO3 rare-earth orthoborates are herein reported up to 17.4(2) and 13.4(2) GPa respectively. The subsequent determination of the room-temperature pressure-volume equations of state is presented and discussed in the context of contemporary publications which contradict the findings of this work. In particular, the isothermal bulk moduli of GdBO3 and YBO3 are found to be 170(13) and 163(13) GPa respectively, almost 50% smaller than recent findings. Our experimental results provide an accurate revision of the high-pressure compressibility behaviour of GdBO3 and YBO3 which is consistent with the known systematics in isomor…