Ab initio simulations of α - and β -ammonium carbamate (NH4 · NH2CO2), and the thermal expansivity of deuterated α -ammonium carbamate from 4.2 to 180 K by neutron powder diffraction
Experimental and computational studies of ammonium carbamate have been carried out, with the objective of studying the elastic anisotropy of the framework manifested in (i) the thermal expansion and (ii) the compressibility; furthermore, the relative thermodynamic stability of the two known polymorphs has been evaluated computationally. Using high-resolution neutron powder diffraction data, the crystal structure of α -ammonium carbamate (ND4 · ND2CO2) has been refined [space group Pbca, Z = 8, with a = 17.05189 (15), b = 6.43531 (7), c = 6.68093 (7) Å and V = 733.126 (9) Å 3 at 4.2 K] and th...
Source: Acta Crystallographica Section B - April 30, 2022 Category: Chemistry Authors: Howard, C.M. Wood, I.G. Knight, K.S. Fortes, A.D. Tags: powder diffraction thermal expansion DFT neutron diffraction negative linear compressibility ammonium carbamate research papers Source Type: research
Single-crystal-to-single-crystal phase transition of 18 β -glycyrrhetinic acid isopropyl ester
Due to the destruction of the integrity of the parent crystal, single-crystal-to-single-crystal phase transition in organic compounds is still a relatively rare phenomenon. The phase transition in glycyrrhetinic acid isopropyl ester is triggered by temperature change. The increasing volume of the isopropyl substituent as a result of increasing temperature forces a remodelling of the structural motifs. These changes cause a single-crystal-to-single-crystal phase transition. The low-temperature form is isostructural with glycyrrhetinic acid methanol solvate, while the high-temperature phase is isostructural with the ethyl es...
Source: Acta Crystallographica Section B - April 30, 2022 Category: Chemistry Authors: Langer, D. Wicher, B. Tykarska, E. Tags: triterpene phase transition glycyrrhetinic acid crystal structure differential scanning calorimetry DSC research papers Source Type: research
N-Iodosaccharin – pyridine co-crystal system under pressure: experimental evidence of reversible twinning
This work presents a single-crystal X-ray diffraction study of an organic co-crystal composed of N-iodosaccharin and pyridine (NISac · py) under hydrostatic pressure ranging from 0.00 (5) GPa to 4.5 (2) GPa. NISac · py crystallizes in the monoclinic system (space group B21/e). The unconventional setting of the space group is adopted (the conventional setting is P21/c, No. 14) to emphasise the strongly pseudo-orthorhombic symmetry of the lattice, with a β angle very close to 90 ° . The crystal structure contains one molecule each of N-iodosaccharin (NISac) and pyridine (py) in the asymmetric unit (Z ′ = 1)...
Source: Acta Crystallographica Section B - April 29, 2022 Category: Chemistry Authors: Vijayakumar-Syamala, V. Aubert, E. Deutsch, M. Wenger, E. Dhaka, A. Fourmigu é , M. Nespolo, M. Espinosa, E. Tags: intermolecular interactions high-pressure studies single-crystal X-ray diffraction twinning research papers Source Type: research
Structural properties of defective (CH3NH3)2Cu(Cl1 – xBrx)4 compounds
The crystal structures of (CH3NH3)2Cu(Cl1 – xBrx)4 compounds have been investigated by means of synchrotron powder X-ray diffraction and pair distribution function analysis at room temperature. As a result, new insights are gained about the structural properties of these compounds, suggesting a monoclinic symmetry (space group No. 14: P21/c – C_{2h}^{5}) induced by the co-operative orbital ordering produced by the Jahn – Teller distortion characterizing the 3d9 Cu2+ ion. In contrast to previous studies, a significant amount of vacancies is found at halogen positions, a feature that can be likely ascribed to the synth...
Source: Acta Crystallographica Section B - April 21, 2022 Category: Chemistry Authors: Martinelli, A. Ray, A. Abdelhady, A.L. Locardi, F. Tags: PXRD synchrotron Rietveld distribution function analysis copper research papers Source Type: research
Hans-Beat B ü rgi in Strasbourg – the story of an encounter
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - April 1, 2022 Category: Chemistry Authors: Lehn, J.-M. Tags: Hans-Beat B ü rgi Strasbourg memories opinions Source Type: research
Circumventing a challenging aspect of crystal structure determination from powder diffraction data
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - April 1, 2022 Category: Chemistry Authors: Harris, K.D.M. Tags: crystal structure determination powder diffraction data indexing unit-cell determination global optimization scientific commentaries Source Type: research
Metastable disordered phase in flash-frozen Prussian Blue analogues
A new metastable phase in flash-frozen disordered Prussian blue analogues is reported. The phase is characterised by the appearance of diffuse scattering clouds and the reduction of the local structure symmetry: from cubic to a tetragonal or lower space group. The phase transition is characterised by the translational modulation of the structure and is likely caused by the freezing of the water confined in the pores of the structure. (Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - March 31, 2022 Category: Chemistry Authors: Kholina, Y. D ö ssegger, J. Weber, M.C. Simonov, A. Tags: diffuse scattering Prussian blue analogues metastable phase transition IR spectroscopy research papers Source Type: research
Bone hierarchical structure: spatial variation across length scales
Bone is a complex hierarchical biomineralized material, which is special amongst biominerals because it is replete with cells, namely, osteocytes. While bone has been scrutinized for centuries, many questions remain open and new research hints that the ultrastructure of bone, encompassing both the bone matrix itself and the embedded cell network, is much more heterogeneous than hitherto realized. A number of these new findings have been made thanks to the enormous developments in X-ray imaging that have occurred in recent decades, and there is promise that they will also allow many of the remaining open questions to be add...
Source: Acta Crystallographica Section B - March 31, 2022 Category: Chemistry Authors: Wittig, N.K. Birkedal, H. Tags: bone biomineralization hierarchical material X-ray imaging topical reviews Source Type: research
A new linear phenyloxazole – benzothiadiazole luminophore: crystal growth, structure and fluorescence properties
A new linear luminophore consisting of five conjugated units of oxazole, phenylene and a central benzothiadiazole fragment, 4,7-bis[4-(1,3-oxazol-5-yl)phenyl]-2,1,3-benzothiadiazole, has been synthesized and characterized. Needle-like single-crystal samples up to 10 mm in length were obtained by physical vapor transport. The crystal structure was determined at 95 K and 293 K using single-crystal X-ray diffraction. With decreasing temperature, the space group P21/n does not change, but the unit-cell volume of the crystal decreases. The presence of intra- and intermolecular hydrogen bonds was established. Melting...
Source: Acta Crystallographica Section B - March 31, 2022 Category: Chemistry Authors: Postnikov, V.A. Sorokina, N.I. Kulishov, A.A. Lyasnikova, M.S. Sorokin, T.A. Freidzon, A.Y. Stepko, A.S. Borshchev, O.V. Skorotetsky, M.S. Surin, N.M. Svidchenko, E.A. Ponomarenko, S.A. Tags: linear conjugated oligomer oxazole benzothiadiazole crystal growth physical vapor transport single-crystal X-ray diffraction hydrogen bonds liquid-crystal mesophase fluorescence large Stokes shift research papers Source Type: research
Response to comment on Properties and interactions – melting point of tribromobenzene isomers
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - March 30, 2022 Category: Chemistry Authors: Bujak, M. Podsiad ł o, M. Katrusiak, A. Tags: isomers melting point molecular symmetry cohesion forces letters to the editor Source Type: research
Comment on the article Properties and interactions – melting point of tribromobenzene isomers
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - March 30, 2022 Category: Chemistry Authors: van de Streek, J. Tags: isomers melting point molecular symmetry number cohesive energy letters to the editor Source Type: research
Powder X-ray diffraction as a powerful tool to exploit in organic electronics: shedding light on the first N,N ′ ,N ′ ′ -trialkyldiindolocarbazole
The first crystal structure of a fully N-alkylated diindolocarbazole derivative, namely, 5,8,14-tributyldiindolo[3,2-b;2 ′ ,3 ′ -h]carbazole (1, C36H39N3), has been determined from laboratory powder X-ray diffraction (PXRD) data. A complex trigonal structure with a high-volume unit cell of 12987 Å 3 was found, with a very long a(=b) [52.8790 (14) Å ] and a very short c [5.36308 (13) Å ] unit-cell parameter (hexagonal setting). The detailed analysis of the intermolecular interactions observed in the crystal structure of 1 highlights its potential towards the implementation of this core as a semico...
Source: Acta Crystallographica Section B - March 29, 2022 Category: Chemistry Authors: Vilche, A. Bujald ó n, R. Alcob é , X. Velasco, D. Puigjaner, C. Tags: organic semiconductor OTFT crystal structure determination powder X-ray diffraction SDPD TOPAS diindolocarbazole research papers Source Type: research
A four-dimensional model for the Ba – Ti – O dodecagonal quasicrystal
A four-dimensional (4D) model is presented of the first oxide dodecagonal quasicrystal found in a Ba – Ti – O ultra-thin film on a Pt(111) single-crystal substrate. The 4D model, with a 4D dodecagonal lattice constant ad = 8.39 Å , was derived by considering a tile decoration model of dodecagonal Niizeki – G ä hler tiling composed of squares, triangles and 30 ° rhombuses. The model consists of four kinds of occupation domain, and 4D positional vectors defining the shape of each occupation domain are given. Moreover, the atomic arrangement of two Ba – Ti – O periodic approximants, the sigma-phase approxi...
Source: Acta Crystallographica Section B - March 24, 2022 Category: Chemistry Authors: Yamada, T. Tags: quasicrystal approximant high-dimensional crystal oxide thin film research papers Source Type: research
π -Hole bonding in a new co-crystal hydrate of gallic acid and pyrazine: static and dynamic charge density analysis
This study presents the first comparison between an XWR and a MEM experimental electron-density determination. (Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - March 23, 2022 Category: Chemistry Authors: Pal, R. Jelsch, C. Momma, K. Grabowsky, S. Tags: cocrystal hydrate π -hole carbon bonding static charge density dynamic charge density quantum crystallography research papers Source Type: research
Jack David Dunitz (1923 – 2021) and chemical crystallography
(Source: Acta Crystallographica Section B)
Source: Acta Crystallographica Section B - March 22, 2022 Category: Chemistry Authors: B ü rgi, H.-B. Tags: obituary chemical crystallography X-ray crystallography structure correlation obituaries Source Type: research
