Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structure-property relations and the use of databases of crystal structures, are published.

Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in a broad sense. Understanding the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often key to grasping physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B serves as a forum for the publication of such contributions. The journal welcomes scientific developments based on both experimental studies and theoretical approaches, including crystal-structure prediction, structure-property relations, and the utilization of databases of crystal structures.

《Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials》期刊发表与化合物和材料的结构科学相关的科学文章。原子排列的知识，包括其时间变化及对温度和压力的依赖，通常是理解物理和化学现象的关键，并且对新材料和超分子器件的设计至关重要。《Acta Crystallographica B》是发表此类贡献的论坛。期刊接受基于实验研究的科学发展以及基于理论方法的研究，包括晶体结构预测、结构-性质关系和晶体结构数据库的使用。

Acta Crystallographica Section B: Structural Science

We briefly describe the structures of open-framework metal phosphates with different dimensionalities, such as the one-dimensional linear-chain and ladder structures, two-dimensional layer structures and three-dimensional structures with channels. We demonstrate the role of the zero-dimensional four-membered ring monomer and of the one-dimensional ladder structure as the starting building units or synthons involved in the formation of the complex architectures. Thus, we show how the one-dimensional ladder structure transforms to two- and three-dimensional structures under mild conditions. The two-dimensional layer structures also transform to three-dimensional structures, while the zero-dimensional monomer transforms to layered and three-dimensional structures under ordinary reaction conditions. These transformations provide an insight into the possible pathways involved in the building up of the complex structures of metal phosphates. The isolation of amine phosphates during the hydrothermal synthesis of metal phosphates and also the facile reactions between amine phosphates and metal ions to yield a variety of open-framework materials have thrown light on the mechanism of formation and design of these structures. The existence of a hierarchy of open-framework metal oxalates and their ready formation by employing amine oxalates as intermediates provides additional support to the observations made earlier with regard to the phosphates.

C. N. R. Rao

Srinivasan Natarajan

Amitava Choudhury

S. Neeraj

R. Vaidhyanathan

Acta Crystallographica Section B Structural Science

Synthons and design in metal phosphates and oxalates with open architectures

金属磷酸盐和草酸盐中开放结构中的合成子和设计

One of the main phases formed at the beginning of the carbonation reaction of cementitious building materials is the calcium hemicarboaluminate (abbreviated as Hc). This AFm (shorthand for hydrated calcium aluminate phases structurally related to hydrocalumite) phase was synthesized, crystallized and then studied by synchrotron X-ray powder diffraction and micro-Raman spectroscopy. At room temperature and standard experimental conditions two major cementitious phases were detected, the Hc phase (as a major phase) and carbonated calcium hemicarboaluminate (abbreviated as cHc). By increasing the temperature the Hc form transforms into cHc. The crystal structures of these important AFm phases were successfully solved and refined in the R3c space group of the trigonal crystal system. Hc has the unit-cell parameters a = 5.7757 (1) and c = 48.812 (2) Å, and cHc the unit-cell parameters a = 5.7534 (1) and c = 46.389 (1) Å. The two crystal structures are composed of positively charged main layers, [Ca(4)Al(2)(OH)(12)](2+), and negatively charged interlayers, [OH(2n)(CO(3))(1 - n)·4H(2)O](2-). The structure of the main layers is typical of the AFm family. Conversely, the interlayer region has a characteristic structure built up from water molecules and statistically distributed anions. In the interlayer, the Hc carbonate and hydroxyl anions are distributed in a 0.25:0.5 ratio, whereas the ratio of the anions in the cHc interlayers is 0.4:0.2.

Tomče Runčevski

Robert E. Dinnebier

Oxana V. Magdysyuk

Herbert Pöllmann

Crystal structures of calcium hemicarboaluminate and carbonated calcium hemicarboaluminate from synchrotron powder diffraction data

钙半碳铝酸盐和碳酸钙半碳铝酸盐的晶体结构：来自同步辐射粉末衍射数据的研究。

A detailed analysis of correlations between structural features and cation conductivity is performed for KAlO(2) polymorphs in a wide temperature range of 300-1023 K. To explore the migration maps of K(+) cations we have used neutron diffraction data for low- and high-temperature KAlO(2) polymorphs and applied for the first time a novel algorithm based on the natural tiling concept and implemented it into the program package TOPOS. Five independent elementary channels for the K(+) cation migration have been revealed whose cross-sections were found to be essentially different in the low-temperature form, indicating a high anisotropy of the cation conductivity. During the transition to the cubic high-temperature phase all five channels become equivalent with sharply increased cross-sections that account for the jump-like increase of the cation conductivity and gives rise to its three-dimensional character.

Vladimir I. Voronin

Georgi Sh. Shekhtman

Vladislav A. Blatov

The natural tiling approach to cation conductivity in KAlO2 polymorphs

KAlO2多晶型物中阳离子导电性的自然平铺方法

The single-crystal diffraction structures of 38 salt forms of the base tyramine (4-hydroxyphenethylamine) are reported for the first time. Together with literature examples, these structures are discussed with respect to cation conformation, cation packing, hydrogen bonding and hydrate formation. It is found that isostructural cation packing can occur even with structurally different anions, with different hydration states and with different hydrogen bonding. Hydrate formation is found to be more likely both (i) when there is an increase in the total number of potential hydrogen bond acceptor and donor atoms; and (ii) when the ratio of potential hydrogen bond donor to acceptor atoms is low.

Naomi E. B. Briggs

Alan R. Kennedy

Catriona A. Morrison

42 salt forms of tyramine: structural comparison and the occurrence of hydrate formation

42种酪胺盐形式：结构比较及水合物形成情况

Two flexible molecules, biuret and 6-acetamidouracil, were cocrystallized with 5-fluorocytosine to study their conformational preferences. In the cocrystal with 5-fluorocytosine (I), biuret exhibits the same conformation as in its hydrate. In contrast, 6-acetamidouracil can adopt two main conformations depending on its crystal environment: in crystal (II) the trans form characterized by an intramolecular hydrogen bond is observed, while in the cocrystal with 5-fluorocytosine (III), the complementary binding induces the cis form. Three cocrystals of 6-methylisocytosine demonstrate that complementary binding enables the crystallization of a specific tautomer. In the cocrystals with 5-fluorocytosine, (IV a ) and (IV b ), only the 3 H tautomer of 6-methylisocytosine is present, whereas in the cocrystal with 6-aminoisocytosine, (V), the 1 H tautomeric form is adopted. The complexes observed in the cocrystals are stabilized by three hydrogen bonds similar to those constituting the Watson–Crick C·G base pair.

Maya Tutughamiarso

Ernst Egert

Cocrystals of 5-fluorocytosine. II. Coformers with variable hydrogen-bonding sites

5-氟胞嘧啶共晶体。II. 具有可变氢键位点的共组分

Bond-valence parameters r0 and b have been re-determined for TeIV—O: r0 = 1.9605 Å, b = 0.41; TeVI—O: r0 = 1.921 Å, b = 0.56; and TeIV—Cl: r0 = 2.3115 Å, b = 0.555. Bond distance data from 208 independent TeIV—O polyhedra, 118 TeVI—O polyhedra and 26 TeIV—Cl polyhedra were used, and all neighbours out to 3.5 Å were included. Root-mean square deviations of bond-valence sums on Te from ideal values were 0.1934, 0.1939 and 0.0865 v.u. The good fit for TeIV—O over a range of Te coordination numbers from 3 to 12 demonstrates that there is no essential difference in character between short `primary' Te—O bonds, oriented away from the Te lone pair, and longer `secondary' Te—O bonds on the same side of the Te atom as the lone pair. Comparison of bond-valence sums for Te—O polyhedra obtained using the new parameters with those calculated using earlier literature values shows that the new parameters give a narrower spread of calculated bond-valence sums, which means much closer to the formal valence for both oxidation states of tellurium.

Stuart J. Mills

Andrew G. Christy

Revised values of the bond-valence parameters for TeIV—O, TeVI—O and TeIV—Cl

TeIV—O、TeVI—O和TeIV—Cl键价参数的修订值

Five new compounds belonging to the phosphoric triamide family have been synthesized: two of them with the formula XC(O)NHP(O)Y [X = CF3 (1) and CClF2 (2), Y = NHCH2C(CH3)2CH2NH] involving a 1,3-diazaphosphorinane ring part, and three 2,6-Cl2C6H3C(O)NHP(O)Z2 phosphoric triamides [Z = NHC(CH3)3 (3), N(CH3)(C6H11) (4) and N(CH3)(CH2C6H5) (5)]. The characterization was performed by 31P{1H}, 1H, 13C NMR, IR spectroscopy besides 19F NMR for fluorine containing compounds (1) and (2), and X-ray single-crystal structure analysis for (1), (3), (4) and (5). In each molecule the P atom has a distorted tetrahedral environment. The N atoms bonded to P atom have mainly sp2 character with a very slight tendency to a pyramidal coordination for some amido groups. Different types of N—H⋯O hydrogen bonds have been analyzed for (1), (3), (4) and (5) and 118 other structures (including 194 hydrogen bonds) deposited in the Cambridge Structural Database, containing either C(O)—NH—P(O)[N(C)(C)]2 or C(O)—NH—P(O)[NH(C)]2. The participation of NCP—H⋯O=P [NCP = the nitrogen atom of the C(O)—NH—P(O) fragment], N—H⋯O=P, N—H⋯O=C and NCP—H⋯O=C hydrogen bonds in different hydrogen-bonded motifs are discussed. Moreover, the involvement of the O atoms of C=O or P=O in the [NCP—H][N—H]⋯O=P, [N—H]2⋯O=P, [N—H]2⋯O=C and [N—H]3⋯O=C groups are considered. A histogram of N⋯O distances, the distribution of N—H⋯O angles and the scatterplot of N—H⋯O angles versus N⋯O distances are studied.

Mehrdad Pourayoubi

Maryam Toghraee

Vladimir Divjakovic

Arie van der Lee

Teresa Mancilla Percino

Marco A. Leyva Ramírez

Anahid Saneei

Analysis of N—H...O hydrogen bonds in new C(O)—NH—P(O)-based phosphoric triamides and analogous structures deposited in the Cambridge Structural Database

基于C(O)—NH—P(O)的新型磷酸三酰胺及其类似结构中N—H...O氢键的分析——来自剑桥结构数据库的数据

Dynamic model densities according to Mondal et al. [(2012), Acta Cryst. A68, 568–581] are presented for independent atom models (IAM), IAMs after high-order refinements (IAM-HO), invariom (INV) models and multipole (MP) models of α-glycine, dl-serine, l-alanine and Ala–Tyr–Ala at T ≃ 20 K. Each dynamic model density is used as prior in the calculation of electron density according to the maximum entropy method (MEM). We show that at the bond-critical points (BCPs) of covalent C—C and C—N bonds the IAM-HO and INV priors produce reliable MEM density maps, including reliable values for the density and its Laplacian. The agreement between these MEM density maps and dynamic MP density maps is less good for polar C—O bonds, which is explained by the large spread of values of topological descriptors of C—O bonds in static MP densities. The density and Laplacian at BCPs of hydrogen bonds have similar values in MEM density maps obtained with all four kinds of prior densities. This feature is related to the smaller spatial variation of the densities in these regions, as expressed by small magnitudes of the Laplacians and the densities. It is concluded that the use of the IAM-HO prior instead of the IAM prior leads to improved MEM density maps. This observation shows interesting parallels to MP refinements, where the use of the IAM-HO as an initial model is the accepted procedure for solving MP parameters. A deconvolution of thermal motion and static density that is better than the deconvolution of the IAM appears to be necessary in order to arrive at the best MP models as well as at the best MEM densities.

Siriyara Jagannatha Prathapa

Swastik Mondal

Sander van Smaalen

Electron densities by the maximum entropy method (MEM) for various types of prior densities: a case study on three amino acids and a tripeptide

最大熵方法（MEM）在不同先验密度下的电子密度：以三种氨基酸和一个三肽为例的研究

The structural details of ferroelectric surfaces influence the effect of ferroelectric polarization on surface chemistry, and it is important to understand and control defect functionality as well as identify adsorption sites in ferroelectric materials. Ferroelectric domain polarization has been found to have a significant effect on surface properties and interactions. Here, both the structure and the presence of local electric fields are examined simultaneously. The surface structure and ferroelectric domain orientation are controlled while molecular adsorption effects are quantified. We use scanning tunneling microscopy (STM) to determine the surface and electronic effects of polarization–gas interactions on a model ferroelectric surface, BaTiO3 (001).

Laura Y. Kraya

Ramsey Kraya

Polarization dependence of molecular adsorption on ferroelectrics

铁电体上分子吸附的偏振依赖性

Invarioms are aspherical atomic scattering factors that enable structure refinement of more accurate and more precise geometries than refinements with the conventional independent atom model (IAM). The use of single-crystal X-ray diffraction data of a resolution better than sin θ/λ = 0.6 Å−1 (or d = 0.83 Å) is recommended. The invariom scattering-factor database contains transferable pseudoatom parameters of the Hansen–Coppens multipole model and associated local atomic coordinate systems. Parameters were derived from geometry optimizations of suitable model compounds, whose IUPAC names are also contained in the database. Correct scattering-factor assignment and orientation reproduces molecular electron density to a good approximation. Molecular properties can hence be derived directly from the electron-density model. Coverage of chemical environments in the invariom database has been extended from the original amino acids, proteins and nucleic acid structures to many other environments encountered in organic chemistry. With over 2750 entries it now covers a wide sample of general organic chemistry involving the elements H, C, N and O, and to a lesser extent F, Si, S, P and Cl. With respect to the earlier version of the database, the main modification concerns scattering-factor notation. Modifications improve ease of use and success rates of automatic geometry-based scattering-factor assignment, especially in condensed hetero-aromatic ring systems, making the approach well suited to replace the IAM for structures of organic molecules.

Publication Information	Publisher: International Union of Crystallography，Publishing cycle: Bimonthly，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 1983，Proportion of original research papers: 100.00%，Self Citation Rate:7.70%， Gold OA Rate: 28.57%
Average review cycle	网友分享经验：较慢,6-12周
Average recruitment ratio	网友分享经验：较易

Acta Crystallographica Section B: Structural Science

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