High-pressure and environment effects in selenourea and its labile crystal field around molecules
Ambient-pressure trigonal phase α of selenourea SeC(NH2)2 is noncentrosymmetric, with high Z ′ = 9. Under high pressure it undergoes several intriguing transformations, depending on the pressure-transmitting medium and the compression or recrystallization process. In glycerine or oil, α -SeC(NH2)2 transforms into phase β at 0.21 GPa; however in water, phase α initially increases its volume and can be compressed to 0.30 GPa due to the formation of α -SeC(NH2)2 · xH2O. The single crystals of α -SeC(NH2)2 and of its partial hydrate α -SeC(NH2)2 · xH2O are shattered by pressure-induced transitions. Single cr...
Source: Acta Crystallographica Section B - May 27, 2021 Category: Chemistry Authors: Roszak, K. Katrusiak, A. Tags: high pressure crystallization polymorphs phase transitions hydrate research papers Source Type: research
Impact of synchrotron X-ray radiation damage on a molecular ferroelectric crystal
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - May 27, 2021 Category: Chemistry Authors: Collings, I.E. Tags: radiation damage molecular crystal phase transition thermal expansion single-crystal diffraction scientific commentaries Source Type: research
Unusual thermal expansion in organic molecular crystals: a rare phenomenon
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - May 25, 2021 Category: Chemistry Authors: Das, D. Tags: organic molecular crystal thermal expansion X-ray diffraction crystal engineering scientific commentaries Source Type: research
Clarification of the ordering of intercalated Fe atoms in FexTiS2 and its effect on the magnetic properties
In this study, FexTiS2 structures, synthesized by chemical vapor transport technique at Fe concentrations of 0.05, 0.10, 0.15, 0.20 0.25 and 0.33, were observed three-dimensionally using a transmission electron microscope and their corresponding magnetization values were measured using a superconducting quantum interference device. The results show a switch from local in-plane two-dimensional (2D) ordering of \sqrt 3 a and 2a at concentrations below 0.15 to three-dimensional (3D) ordering of 2a × 2a × 2c at x = 0.20 and 0.25, as well as \sqrt 3 a × \sqrt 3 a × 2c superstructures at x = 0...
Source: Acta Crystallographica Section B - May 22, 2021 Category: Chemistry Authors: Chiew, Y.L. Miyata, M. Koyano, M. Oshima, Y. Tags: intercalation scanning transmission electron microscope transmission electron diffraction magnetism research papers Source Type: research
Structural insight from intermolecular interactions and energy framework analyses of 2-substituted 6,7,8,9-tetrahydro-11H-pyrido[2,1-b]quinazolin-11-ones
The crystal structures of three mackinazolinone derivatives (2-amino-6,7,8,9-tetrahydro-11H-pyrido[2,1-b]quinazolin-11-one at room temperature, and 2-nitro-6,7,8,9-tetrahydro-11H-pyrido[2,1-b]quinazolin-11-one and N-(11-oxo-6,8,9,11-tetrahydro-7H-pyrido[2,1-b]quinazolin-2-yl)benzamide at 100 K) are explored using X-ray crystallography. To delineate the different intermolecular interactions and the respective interaction energies in the crystal architectures, energy framework analyses were carried out using the CE-B3LYP/6-31G(d,p) method implemented in the CrystalExplorer software. In the structures the different molecu...
Source: Acta Crystallographica Section B - May 22, 2021 Category: Chemistry Authors: Tojiboev, A.G. Elmuradov, B.Z. Mouhib, H. Turgunov, K.K. Abdurazakov, A.S. Makhmadiyarova, C.E. Tashkhodjaev, B. Mirzaev, S.Z. Tags: substituted tricyclic quinazolines intermolecular interactions quantum chemical calculations reactivity predictions energy framework mackinazolinone research papers Source Type: research
Structural reasons for the formation of multicomponent products and the influence of high pressure
(S)-( − )-1-Phenylethanaminium 4-(2,4,6-triisopropylbenzoyl)benzoate (S-PEATPBB) undergoes a photochemical reaction in its crystalline form upon UV irradiation and forms three different products: the first product is the result of a Yang cyclization with the participation of the δ -H atom of o-isopropyl (product D) and the second and third products are obtained via a Norrish – Yang reaction with the involvement of the γ -H atom of 2-isopropyl (product P) and 6-isopropyl (product Z). These products are formed in different proportions (D> P>> Z). The path and kinetics of the reaction were monitored step-by-step using c...
Source: Acta Crystallographica Section B - May 21, 2021 Category: Chemistry Authors: Konieczny, K.A. B ą kowicz, J. Paliwoda, D. Warren, M.R. Ciesielski, A. Cyra ń ski, M.K. Turowska-Tyrk, I. Tags: crystal structure high-pressure structure photochemistry X-ray structure analysis solid-state reaction research papers Source Type: research
Modelling the structural variation of quartz and germanium dioxide with temperature by means of transformed crystallographic data
The pseudocubic (PC) parameterization of O4 tetrahedra [Reifenberg& Thomas (2018). Acta Cryst. B74, 165 – 181] is applied to quartz (SiO2) and its structural analogue germanium dioxide (GeO2). In α -quartz and GeO2, the pseudocubes are defined by three length parameters, aPC, bPC and cPC, together with an angle parameter α PC. In β -quartz, α PC has a fixed value of 90 ° . For quartz, the temperature evolution of parameters for the pseudocubes and the silicon ion network is established by reference to the structural refinements of Antao [Acta Cryst. (2016), B72, 249 – 262]. In α -quartz, the curve-fitting employe...
Source: Acta Crystallographica Section B - May 20, 2021 Category: Chemistry Authors: Fricke, M. Thomas, N.W. Tags: quartz pseudocubic INA tilt angle structure prediction GeO2 research papers Source Type: research
The classification of 1D `perovskites'
There has been a huge amount of interest in perovskites recently and new structures of hybrid perovskites are frequently reported. The classification of perovskites has been unambiguous in the discussion of 3D and layered 2D perovskites due to the dimensional constraints. However, in 1D perovskites, the additional degrees of freedom have resulted in a large number of possible structural configurations. The new proposed notation aims to classify these structures based on the connectivity of the octahedra of the perovskite, which has a periodic repeating pattern. However, the notation should be restricted to simple 1D perovs...
Source: Acta Crystallographica Section B - May 20, 2021 Category: Chemistry Authors: Wong, W.P.D. Hanna, J.V. Grimsdale, A.C. Tags: perovskite notation classification research papers Source Type: research
Thermal expansion and phase transformation in the rare earth di-titanate (R2Ti2O7) system
Characterization of the thermal expansion in the rare earth di-titanates is important for their use in high-temperature structural and dielectric applications. Powder samples of the rare earth di-titanates R2Ti2O7 (or R2O3 · 2TiO2), where R = La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Y, which crystallize in either the monoclinic or cubic phases, were synthesized for the first time by the solution-based steric entrapment method. The three-dimensional thermal expansions of these polycrystalline powder samples were measured by in situ synchrotron powder diffraction from 25 ° C to 1600 ° C in air, nearly 600 ° C higher than other in...
Source: Acta Crystallographica Section B - May 20, 2021 Category: Chemistry Authors: Hulbert, B.S. McCormack, S.J. Tseng, K.-P. Kriven, W.M. Tags: rare earth di-titanate X-ray diffraction neutron diffraction thermal expansion phase transition La2Ti2O7 high-temperature research papers Source Type: research
Hydrogen-bond directionality and symmetry in [C(O)NH](N)2P(O)-based structures: a comparison between X-ray crystallography data and neutron-normalized values, and evaluation of reliability
For [C(O)NH](N)2P(O)-based structures, the magnitude of the differences in the N — H...O, H...O=P and H...O=C angles has been evaluated when the N — H bond lengths, determined by X-ray diffraction, were compared to the neutron normalized values and the maximum percentage difference was obtained, i.e. about 3% for the angle even if the N — H bond lengths have a difference of about 30% (0.7 Å for the X-ray and 1.03 Å for the neutron-normalized value). The symmetries of the crystals are discussed with respect to the symmetry of the molecules, as well as to the symmetry of hydrogen-bonded motifs, and the role o...
Source: Acta Crystallographica Section B - May 19, 2021 Category: Chemistry Authors: Taherzadeh, M. Pourayoubi, M. Vahdani Alviri, B. Shoghpour Bayraq, S. Ariani, M. Ne č as, M. Du š ek, M. Eigner, V. Amiri Rudbari, H. Bruno, G. Mancilla Percino, T. Leyva-Ram í rez, M.A. Damodaran, K. Tags: phosphoric triamide X-ray diffraction neutron normalization symmetry Cambridge Structural Database lone electron pair research papers Source Type: research
Crystal structure of the uranyl arsenate mineral h ü gelite, Pb2(UO2)3O2(AsO4)2(H2O)5, revisited: a correct unit cell, twinning and hydrogen bonding
Revisiting the structure of uranyl arsenate mineral h ü gelite provided some corrections to the available structural data. The previous twinning model (by reticular merohedry) in h ü gelite has been corrected. Twinning of the monoclinic unit cell [a = 7.0189 (7) Å , b = 17.1374 (10) Å , c = 8.1310 (10) Å and β = 108.904 (10) ° ], which can be expressed as a mirror in [100], leads to a pseudo-orthorhombic unit cell (a = 7.019 Å , b = 17.137 Å , c = 61.539 Å and β = 90.02 ° ), which is eight times larger, with respect to the unit-cell volume, than a ...
Source: Acta Crystallographica Section B - May 14, 2021 Category: Chemistry Authors: Pl á š il, J. Pet ř í č ek, V. Š k á cha, P. Tags: h ü gelite uranyl arsenate crystal structure twinning JANA2006 reticular merohedry research papers Source Type: research
Incommensurately modulated crystal structure of α ′ (O ′ 3)-type sodium cobalt oxide NaxCoO2 (x ∼ 0.78)
A single-phase sample of α ′ (O ′ 3)-type layered sodium cobalt oxide NaxCoO2 (x ∼ 0.78) was prepared and its incommensurately modulated crystal structure was analyzed using the (3+1)-dimensional superspace approach to the powder neutron diffraction data. The crystal structure of the cobaltate is accurately described based on the superspace group C2/m( α 0 γ )00, wherein the positions of Na atoms are most significantly modulated in the monoclinic a direction to form an ordered arrangement. Such a displacive modulation causes a quasi-periodic shift of Na atoms from the centers of the NaO6 polyhedra between undulate...
Source: Acta Crystallographica Section B - May 14, 2021 Category: Chemistry Authors: Miyazaki, Y. Igawa, N. Yubuta, K. Tags: sodium cobalt oxide modulated structure powder neutron diffraction superspace group Rietveld analysis research papers Source Type: research
Phase transition in an organic ferroelectric: glycinium phosphite, with and without X-ray radiation damage
Thermal evolution of an organic ferroelectric, namely, glycinium phosphite, was probed by multi-temperature single-crystal diffraction using synchrotron radiation and also by a similar experiment with a laboratory X-ray diffractometer. Both series of measurements showed a transition from the paraelectric to the ferroelectric state at nearly the same temperature, Tc = 225 K. Temperature evolution of the unit-cell parameters and volume are drastically different for the synchrotron and laboratory data. The latter case corresponds to previous reports and shows an expected contraction of the cell on cooling. The data col...
Source: Acta Crystallographica Section B - May 13, 2021 Category: Chemistry Authors: Bogdanov, N.E. Zakharov, B.A. Chernyshov, D. Pattison, P. Boldyreva, E.V. Tags: glycinium phosphite ferroelectric radiation damage spontaneous strain hydrogen bonding research papers Source Type: research
Revisiting stacking interactions in tetrathiafulvalene and selected derivatives using tight-binding quantum chemical calculations and local coupled-cluster method
The engineering of supramolecular architectures needs accurate descriptions of the intermolecular interactions in crystal structures. Tetrathiafulvalene (TTF) is an effective building block used in the construction of promising functional materials. The parallel packing of the neutral TTF – TTF system was studied previously using the high-level quantum chemical method, advancing it as a valuable model system. The recently developed tight-binding quantum chemical method GFN2-xTB and local coupled-cluster method DLPNO-CCSD(T) were used to investigate the stacking interactions of TTF and selected derivatives deposited in th...
Source: Acta Crystallographica Section B - May 13, 2021 Category: Chemistry Authors: Zheng, K. Li, D. Jiang, L. Li, X. Xie, C. Feng, L. Qin, J. Qian, S. Pang, Q. Tags: interaction energy DLPNO-CCSD(T) tetrathiafulvalene energy decomposition dispersion interaction density plot quantum crystallography research papers Source Type: research
A survey of thermal expansion coefficients for organic molecular crystals in the Cambridge Structural Database
Typical ranges of thermal expansion coefficients are established for organic molecular crystals in the Cambridge Structural Database. The CSD Python API is used to extract 6201 crystal structures determined close to room temperature and at least one lower temperature down to 90 K. The data set is dominated by structure families with only two temperature points and is subject to various sources of error, including incorrect temperature reporting and missing flags for variable-pressure studies. For structure families comprising four or more temperature points in the range 90 – 300 K, a linear relationship between u...
Source: Acta Crystallographica Section B - May 13, 2021 Category: Chemistry Authors: Bond, A.D. Tags: thermal expansion molecular crystals Cambridge Structural Database python API research papers Source Type: research
