Comparison of the temperature- and pressure-dependent behavior of the crystal structure of CrAs
The crystal structure of CrAs was investigated using synchrotron X-ray single-crystal diffraction for separate dependences on temperature (30 – 400 K) and on pressure (0 – 9.46 GPa). The isosymmetrical magnetostructural phase transition at TN = 267 K can induce a change in the microstructure by twinning due to a crossing of the orthohexagonal setting of the unit-cell parameter ratio c/b. Within the crystal structure, one particular Cr – Cr distance exhibits anomalous behavior in that it is nearly unaffected by temperature and pressure in the paramagnetic phase, which is stable above 267 K and at high ...
Source: Acta Crystallographica Section B - July 23, 2021 Category: Chemistry Authors: Eich, A. Grzechnik, A. Paulmann, C. M ü ller, T. Su, Y. Wolf, T. Friese, K. Tags: crystal structure low temperature high pressure synchrotron diffraction research papers Source Type: research
Low-temperature phase transition and magnetic properties of K3YbSi2O7
The new ambient-temperature hexagonal (space group P63/mmc) polymorph of tripotassium ytterbium(III) disilicate ( β -K3YbSi2O7) has been synthesized by the high-temperature flux method and subsequently structurally characterized. In the course of the temperature-dependent single-crystal diffraction experiments, a phase transformation of β -K3YbSi2O7 to a novel low-temperature orthorhombic phase ( β ′ -K3YbSi2O7, space group Cmcm) has been observed at about 210 K. β -K3YbSi2O7 is isostructural with K3ErSi2O7, whereas β ′ -K3YbSi2O7 adopts a new type of structure. Both compounds can be built up from a regular al...
Source: Acta Crystallographica Section B - July 23, 2021 Category: Chemistry Authors: Dabi ć , P. Kahlenberg, V. Kr ü ger, B. Rodi ć , M. Kova č , S. Blanu š a, J. Jagli č i ć , Z. Karanovi ć , Lj. Pet ř í č ek, V. Kremenovi ć , A. Tags: alkali rare-earth silicates phase transition magnetic properties crystal field splitting lanthanide silicates research papers Source Type: research
Pressure-induced structural phase transitions in bismuth tungstate Bi2WO6
The pressure-induced structural phase transitions in bismuth tungstate Bi2WO6 have been studied using neutron diffraction and Raman spectroscopy at high pressures up to 7 and 30 GPa, respectively. A rich structural polymorphism was revealed. At P ≃ 3.5 GPa a phase transition from the initial orthorhombic phase of P21ab symmetry to an orthorhombic phase of B2cb symmetry was observed. This transition is caused by the complex spatial rotation of the WO6 octahedra. A subsequent isostructural phase transition to another orthorhombic phase of B2cb symmetry was detected at P ≃ 5.9 GPa, accompanied by changes in bo...
Source: Acta Crystallographica Section B - July 22, 2021 Category: Chemistry Authors: Lis, O.N. Kichanov, S.E. Kozlenko, D.P. Belozerova, N.M. Lukin, E.V. Balakumar, S. Savenko, B.N. Tags: high pressure neutron diffraction Raman spectroscopy structural phase transitions bismuth tungstate structural polymorphism research papers Source Type: research
Bonding features in Appel's salt from the orbital-free quantum crystallographic perspective
Bonding properties in the crystal of 4,5-dichloro-l,2,3-dithiazolium chloride (Appel's salt) were studied using a combination of single-crystal high-resolution X-ray diffraction data and the orbital-free quantum crystallography approach. A QTAIM-based topological model shows the proximity of S — C and S — N bonds to the sesquialteral type and establishes the low S — S bond order in the l,2,3-dithiazolium heterocycle. It is found that the electrostatic potential carries the traces of a common positive area on the junction of interatomic zero-flux surfaces of S1 and S2 atomic basins; meanwhile the exchange energy densi...
Source: Acta Crystallographica Section B - July 22, 2021 Category: Chemistry Authors: Bartashevich, E. Stash, A. Yushina, I. Minyaev, M. Bol'shakov, O. Rakitin, O. Tsirelson, V. Tags: Appel's salt charge density chalcogen bond halogen bond exchange energy density per particle research papers Source Type: research
A new topological semimetal candidate: SmMnBi2
The new compound SmMnBi2 has been synthesized by the self-flux method and shown to crystallize in space group I4/mmm with a = 4.5054 (4) Å , c = 20.5914 (19) Å and Z = 4. Its structure comprises two-dimensional square Mn-nets layers, puckered rock-salt-like SmBi slabs and two-dimensional square Bi-nets layers, alternating along the c axis in an … Mn-net – SmBi slab – Bi-net – SmBi slab – Mn-net … sequence. Surprisingly, the atomic arrangement differs from its neighboring compound EuMnBi2 which has similar layers but with a different stacking arrangement. This gives rise to edge-shared square p...
Source: Acta Crystallographica Section B - July 21, 2021 Category: Chemistry Authors: Krishnan, S. Besara, T. Tags: topological materials Dirac or Weyl semimetals single crystal growth SmMnBi2 research papers Source Type: research
Room-temperature ferroelasticity and unusual sequence of phase transitions in the crystal of (N2H5)3[CdCl5]
On the basis of thermal analysis (DSC, DTA, DTG), single crystal X-ray diffraction experiments, dielectric studies and optical observation, it is found that the (N2H5)3[CdCl5] crystal exhibits several structural phase transitions. At room temperature, the studied crystal exhibits ferroelastic properties and undergoes phase transition from the monoclinic to the orthorhombic phase on heating above 327 K. Upon subsequent cooling, two structural phase transitions at about 323 and 319 K are observed, where the crystal adopts orthorhombic symmetry. The presented phase transitions are unique due to the fact the first heat...
Source: Acta Crystallographica Section B - July 17, 2021 Category: Chemistry Authors: Krawczyk, M.K. Czapla, Z. Ingram, A. Kozdra ś , A. Lis, T. Przes ł awski, J. Tags: phase transition crystal structure electric permittivity ferroelastic domain structure halogenocadmates(II) research papers Source Type: research
Developing orbital-free quantum crystallography: the local potentials and associated partial charge densities
This work extends the orbital-free density functional theory to the field of quantum crystallography. The total electronic energy is decomposed into electrostatic, exchange, Weizsacker and Pauli components on the basis of physically grounded arguments. Then, the one-electron Euler equation is re-written through corresponding potentials, which have clear physical and chemical meaning. Partial electron densities related with these potentials by the Poisson equation are also defined. All these functions were analyzed from viewpoint of their physical content and limits of applicability. Then, they were expressed in terms of ex...
Source: Acta Crystallographica Section B - July 16, 2021 Category: Chemistry Authors: Tsirelson, V. Stash, A. Tags: electron density orbital-free DFT inner-crystal potential decomposition quantum crystallography atoms in molecules research papers Source Type: research
Czochralski growth of mixed cubic sesquioxide crystals in the ternary system Lu2O3 – Sc2O3 – Y2O3
Cubic rare-earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large-size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3 – Sc2O3 – Y2O3 revealing a large range of compositions with melting temperatures below 2200 ° C and a minimum of 2053 ° C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered str...
Source: Acta Crystallographica Section B - July 15, 2021 Category: Chemistry Authors: Kr ä nkel, C. Uvarova, A. Haurat, É . H ü lshoff, L. Br ü tzam, M. Guguschev, C. Kalusniak, S. Klimm, D. Tags: crystal growth optical materials phase diagrams melting points rare earth sesquioxides research papers Source Type: research
Crystal structure and hyperfine interactions of delafossite (CuFeO2) synthesized hydrothermally
The powder specimen of CuFeO2 delafossite was synthesized by a hydrothermal method at 453 K. X-ray diffraction studies confirmed that the obtained pure delafossite phase was a mixture of the 3R and 2H polytypes, predominantly the former. M ö ssbauer spectral analysis revealed the paramagnetic state of the copper ferrite at room temperature. Below 12 K the spectra had complicated shapes of Zeeman sextets. Changes in the character of the hyperfine interactions did not correspond to the data reported for the single-crystal CuFeO2. Magnetization measurements revealed that magnetic transition occurred at N é el temper...
Source: Acta Crystallographica Section B - July 14, 2021 Category: Chemistry Authors: Siedliska, K. Pikula, T. Surowiec, Z. Panek, R. Idczak, R. Tran, V.H. Jartych, E. Tags: delafossite CuFeO2 hydrothermal synthesis ö ssbauer spectroscopy research papers Source Type: research
Recommended X-ray single-crystal structure refinement and Rietveld refinement procedure for tremolite
A detailed description of the structure of the amphibole-supergroup minerals is very challenging owing to their complex chemical composition that renders the process of cation partition extremely difficult, particularly because of the occurrence of multivalent elements. Since amphiboles naturally occur under a fibrous morphology and have largely been used to produce asbestos, there is a growing demand for detailed and accurate structural data in order to study the relationships between structure, composition and toxicity. The present study proposes a recommended refinement procedure for both X-ray single-crystal structure ...
Source: Acta Crystallographica Section B - July 14, 2021 Category: Chemistry Authors: Ballirano, P. Celata, B. Pacella, A. Bosi, F. Tags: structure refinement Rietveld method scattering curves tremolite asbestos research papers Source Type: research
Detailed analysis of deformation potentials with application in orbital-free density functional theory
A detailed analysis of the recently published deformation potentials for application in orbital-free density functional theory is given. Since orbital-free density functional theory is a purely density-based description of quantum mechanics, it may in the future provide itself useful in quantum crystallography as it establishes a direct link between experiment and theory via a single meaningful quantity: the electron density. In order to establish this goal, sufficiently accurate approximations for the kinetic energy have to be found. The present work is a further step in this direction. The so-called deformation potential...
Source: Acta Crystallographica Section B - July 14, 2021 Category: Chemistry Authors: Finzel, K. Tags: quantum crystallography orbital-free density functional theory Pauli potential bifunctional approach deformation potentials research papers Source Type: research
The influence of chalcogen atom on conformation and phase transition in chalcogenazinoquinolinium monoiodides
Crystalline chalcogenazinoquinolinium monoiodides, where the chalcogen atom is oxygen and sulfur, have been studied using a combination of X-ray diffraction, Raman and UV-vis spectroscopies and photoluminescence experimental techniques. Periodic quantum-chemical calculations have been performed to characterize the features of electronic structure and vibrational assignment. X-ray diffraction and Raman spectroscopy experiments consistently reveal phase transition of thiazinoquinolinium monoiodide at low temperatures with the decrease of symmetry to P1. The luminescence study for oxazinoquinolinium monoiodide reveals the exc...
Source: Acta Crystallographica Section B - July 14, 2021 Category: Chemistry Authors: Yushina, I. Krylov, A. Leonidov, I.I Batalov, V. Chen, Y.-S. Wang, S.G. Stash, A. Bartashevich, E. Tags: organic monoiodide phase transition Raman spectroscopy luminescence halogen bond research papers Source Type: research
Positron lifetime spectroscopy of defect structures in Cd1 – xZnxTe mixed crystals grown by vertical Bridgman – Stockbarger method
Positron annihilation lifetime spectroscopy was used to examine grown-in defects in Cd1 – xZnxTe mixed crystals as a function of Zn content (x = 0, 0.07, 0.11, 0.49, 0.9, 0.95, 1) and measuring temperature. All samples were prepared using the high-pressure modified vertical Bridgman – Stockbarger method. The crystal structure and material phase were characterized by X-ray diffraction. The positron lifetime spectra reveal the presence of both open volumes and shallow traps regardless of the sample composition. In particular, both average and bulk lifetimes are found to be much higher in ternary alloys (CdZnTe) than thos...
Source: Acta Crystallographica Section B - July 6, 2021 Category: Chemistry Authors: Gorgol, M. Zaleski, R. Kierys, A. Kami ń ski, D. Strza ł kowski, K. Fedus, K. Tags: cadmium zinc telluride positron lifetime spectroscopy X-ray diffraction shallow positron traps defects research papers Source Type: research
Crystal structure or chemical composition of salt – sugar-based metal – organic frameworks: what are the nonlinear optical properties due to?
In the last few decades optical imaging techniques based on nonlinear optical properties have been of interest for biosensing applications. This work focuses on two isostructural and isomorphous sugar-derived metal – organic frameworks (MOFs) with second-harmonic generation (SHG) properties, in order to investigate their possible application as biosensors in view of their high biocompatibility. Combining 2-deoxy-d-galactose with the metal halogenides CaX2 (X = Br, I), two new isomorphous MOFs of formula [Ca(C6H12O5)2]X2 were obtained and characterized through single-crystal X-ray diffraction. The first-order static hyper...
Source: Acta Crystallographica Section B - July 6, 2021 Category: Chemistry Authors: Marabello, D. Antoniotti, P. Benzi, P. Beccari, F. Canepa, C. Cariati, E. Cioci, A. Lo Presti, L. Tags: metal – organic frameworks nonlinear optical properties second-harmonic generation efficiency isomorphous compounds ab initio calculations structure property relationships research papers Source Type: research
Solid-state electronegativity of atoms: new approaches
Electronegativities (EN) of 65 elements (H to Bi, except lanthanides and noble gases, plus U and Th) in solids were derived from various observed parameters, namely, bond energies in solids, structural geometry, work functions and force constants, yielding a set of internally consistent values. The solid-state electronegativities are generally lower than the conventional (`molecular') values, due to different coordination numbers and electronic structure in a solid versus a molecule; the decrease is stronger for metals than for non-metals, hence binary compounds have a wider EN difference and higher bond polarity (ionicity...
Source: Acta Crystallographica Section B - July 5, 2021 Category: Chemistry Authors: Batsanov, S.S. Batsanov, A.S. Tags: electronegativity force constant high pressure heat of formation solid state research papers Source Type: research
