Pub Date : 2021-09-28DOI: 10.1107/s2052520621008258
Bruno Landeros‐Rivera, J. Contreras‐García, P. Dominiak
The synergy between theory and experiment found in X-ray wavefunction refinement (XWR) makes it one of the most compelling techniques available for chemical physics. The foremost benefit of XWR – obtaining wavefunctions constrained to experimental data – is at the same time its Achilles heel, because of the dependence of the results on the quality of both empirical and theoretical data. The purpose of this work is to answer the following: What is the effect of the refinement strategy and manipulation of input data on the physical properties obtained from XWR? With that in mind, cutoffs based on data resolution and F/σ(F) ratios were applied for both steps of XWR, the Hirshfeld atom refinement (HAR) and the X-ray constrained wavefunction fitting (XCW), for four selected systems: sulfur dioxide, urea, carbamazepine and oxalic acid. The effects of changing the weighting scheme or the method to transform σ(F 2) to σ(F) were also analysed. The results show that while HAR always reaches the same result, XCW is extremely sensitive to crystallographic data manipulation. This is a result of the variability of the experimental uncertainties for different resolution shells, and of not having proper standard uncertainties. Therefore, the use of distinct constraints for each resolution interval in XCW is proposed to fix this instability.
{"title":"The influence of refinement strategies on the wavefunctions derived from an experiment","authors":"Bruno Landeros‐Rivera, J. Contreras‐García, P. Dominiak","doi":"10.1107/s2052520621008258","DOIUrl":"https://doi.org/10.1107/s2052520621008258","url":null,"abstract":"The synergy between theory and experiment found in X-ray wavefunction refinement (XWR) makes it one of the most compelling techniques available for chemical physics. The foremost benefit of XWR – obtaining wavefunctions constrained to experimental data – is at the same time its Achilles heel, because of the dependence of the results on the quality of both empirical and theoretical data. The purpose of this work is to answer the following: What is the effect of the refinement strategy and manipulation of input data on the physical properties obtained from XWR? With that in mind, cutoffs based on data resolution and F/σ(F) ratios were applied for both steps of XWR, the Hirshfeld atom refinement (HAR) and the X-ray constrained wavefunction fitting (XCW), for four selected systems: sulfur dioxide, urea, carbamazepine and oxalic acid. The effects of changing the weighting scheme or the method to transform σ(F\u0000 2) to σ(F) were also analysed. The results show that while HAR always reaches the same result, XCW is extremely sensitive to crystallographic data manipulation. This is a result of the variability of the experimental uncertainties for different resolution shells, and of not having proper standard uncertainties. Therefore, the use of distinct constraints for each resolution interval in XCW is proposed to fix this instability.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73971643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-25DOI: 10.1107/s2052520621008222
M. Souhassou, Iurii Kiblin, M. Deutsch, Ariste Bolivar Voufack, C. Lecomte, N. Claiser
MOLLYNX is a new crystallographic tool developed to access a more precise description of the spin-dependent electron density of magnetic crystals, taking advantage of the richness of experimental information from high-resolution X-ray diffraction (XRD), unpolarized neutron (UND) and polarized neutron diffraction (PND). This new program is based either on the well known Hansen–Coppens multipolar model (MOLLYNX-mult) or on a new expansion over a set of atomic orbitals (MOLLYNX-orb). The main difference between the two models is the basis of the expansion: in MOLLYNX-mult the expansion is over atom centered real spherical harmonics, in MOLLYNX-orb the expansion is over a set of atomic orbitals with which mono and bicentric contributions are calculated. This new approach of MOLLYNX-orb can also be applied to nonmagnetic crystals. This paper summarizes the theoretical ground of two models and describes the first applications to organic, organometallic and inorganic magnetic materials
{"title":"Spin-resolved charge density and wavefunction refinements using MOLLYNX: a review","authors":"M. Souhassou, Iurii Kiblin, M. Deutsch, Ariste Bolivar Voufack, C. Lecomte, N. Claiser","doi":"10.1107/s2052520621008222","DOIUrl":"https://doi.org/10.1107/s2052520621008222","url":null,"abstract":"\u0000 MOLLYNX is a new crystallographic tool developed to access a more precise description of the spin-dependent electron density of magnetic crystals, taking advantage of the richness of experimental information from high-resolution X-ray diffraction (XRD), unpolarized neutron (UND) and polarized neutron diffraction (PND). This new program is based either on the well known Hansen–Coppens multipolar model (MOLLYNX-mult) or on a new expansion over a set of atomic orbitals (MOLLYNX-orb). The main difference between the two models is the basis of the expansion: in MOLLYNX-mult the expansion is over atom centered real spherical harmonics, in MOLLYNX-orb the expansion is over a set of atomic orbitals with which mono and bicentric contributions are calculated. This new approach of MOLLYNX-orb can also be applied to nonmagnetic crystals. This paper summarizes the theoretical ground of two models and describes the first applications to organic, organometallic and inorganic magnetic materials","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90829205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-23DOI: 10.1107/s2052520621008441
Peng Li, Ting Zhang, Li‐Li Li, W. Dong
A family of rare structurally different homometal multinuclear CuII bis(salamo)-based complexes, [Cu4(L)2(MeOH)2](ClO4)2·2MeOH (1), [Cu4(L)2(EtOH)2](NO3)2·2EtOH (2) and [Cu2(HL)(EtOH)Br2]·CHCl3 (3), has been successfully synthesized by the reactions of cupric salts with a bis(salamo)-based multidentate chelate ligand (H3 L). The salamo-based ligand [R-CH=N—O—(CH2) n —O—N=CH—R] is a new type of salen-based analog. Complexes (1) and (2) are isostructural structures, and crystallize in monoclinic space group P21/n with centrosymmetric spiral structures, where the main structures contain two fully deprotonated ligand (L)3− units, a charged tetranuclear CuII folding center and two coordinated solvent molecules. Complex (3) crystallizes in monoclinic space group Cc and consists of two CuII cations, one incompletely deprotonated ligand (HL)2− unit and one coordinated ethanol molecule, and forms a novel homo-binuclear CuII complex structure due to Br− counter anions. Complexes (1)–(3) have zero-dimensional cluster-based structures and are further assembled into three-dimensional frameworks via intermolecular interactions. Because of the different solvents and counter anions which have a significant influence on the structures of complexes (1)–(3), the interactions were quantitatively evaluated by Hirshfeld surfaces analyses. Complexes (1)–(3) have been characterized by elemental analyses, IR spectra, UV–vis spectra and X-ray crystallography analyses. In addition, fluorescence properties are evaluated and DFT calculations are performed.
{"title":"Self-assembling of three rare structurally various homomultinuclear CuII complexes derived from a bis(salamo)-based multioxime ligand","authors":"Peng Li, Ting Zhang, Li‐Li Li, W. Dong","doi":"10.1107/s2052520621008441","DOIUrl":"https://doi.org/10.1107/s2052520621008441","url":null,"abstract":"A family of rare structurally different homometal multinuclear CuII bis(salamo)-based complexes, [Cu4(L)2(MeOH)2](ClO4)2·2MeOH (1), [Cu4(L)2(EtOH)2](NO3)2·2EtOH (2) and [Cu2(HL)(EtOH)Br2]·CHCl3 (3), has been successfully synthesized by the reactions of cupric salts with a bis(salamo)-based multidentate chelate ligand (H3\u0000 L). The salamo-based ligand [R-CH=N—O—(CH2)\u0000 n\u0000 —O—N=CH—R] is a new type of salen-based analog. Complexes (1) and (2) are isostructural structures, and crystallize in monoclinic space group P21/n with centrosymmetric spiral structures, where the main structures contain two fully deprotonated ligand (L)3− units, a charged tetranuclear CuII folding center and two coordinated solvent molecules. Complex (3) crystallizes in monoclinic space group Cc and consists of two CuII cations, one incompletely deprotonated ligand (HL)2− unit and one coordinated ethanol molecule, and forms a novel homo-binuclear CuII complex structure due to Br− counter anions. Complexes (1)–(3) have zero-dimensional cluster-based structures and are further assembled into three-dimensional frameworks via intermolecular interactions. Because of the different solvents and counter anions which have a significant influence on the structures of complexes (1)–(3), the interactions were quantitatively evaluated by Hirshfeld surfaces analyses. Complexes (1)–(3) have been characterized by elemental analyses, IR spectra, UV–vis spectra and X-ray crystallography analyses. In addition, fluorescence properties are evaluated and DFT calculations are performed.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77808369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-22DOI: 10.1107/s2052520621008891
Dušica Jovanović, D. Zagorac, B. Matović, A. Zarubica, J. Zagorac
Recent studies of TiO2/TiS2 nanostructures with various morphologies have been reported, usually showing improved properties with applications from electronics and catalysis to solar cells and medicine. However, there is a limited number of studies on the crystal structures of TiO2/TiS2 compounds with corresponding properties. In this research, relevant crystal structures of TiO1–x S x (x = 0, 0.25, 0.5, 0.75 and 1) solid solutions were investigated using an ab initio method. For each composition, crystal structures adopting anatase, rutile and CdI2 structure type were calculated on LDA-PZ and GGA-PBE levels of theory. Novel phase transitions and predicted structures are presented, and apart from several interesting metastable structures, a very interesting pressure-induced phase transition is found in the TiOS compound. Furthermore, electronic properties were studied through the dependence of semiconducting properties on dopant concentration. The first description of the electronic properties of the mixed TiO1–x S x compounds in crystal form has been presented, followed by a detailed study of the structure–property relationship, which will possibly have numerous industrial and technological applications.
近年来对不同形态的TiO2/TiS2纳米结构的研究已经被报道，通常在电子、催化、太阳能电池和医学等领域显示出改进的性能。然而，对具有相应性质的TiO2/TiS2化合物晶体结构的研究数量有限。本研究采用从头算方法研究了TiO1-x sx (x = 0、0.25、0.5、0.75和1)固溶体的相关晶体结构。在LDA-PZ和GGA-PBE理论水平上计算了每种成分采用锐钛矿、金红石和CdI2结构类型的晶体结构。提出了新的相变和预测结构，除了几个有趣的亚稳结构外，在TiOS化合物中发现了一个非常有趣的压力诱导相变。此外，通过半导体性质与掺杂浓度的关系研究了电子性质。本文首先描述了晶体形式的混合TiO1-x - S - x化合物的电子性质，然后对结构-性能关系进行了详细的研究，这可能会有许多工业和技术应用。
{"title":"Anion substitution and influence of sulfur on the crystal structures, phase transitions, and electronic properties of mixed TiO2/TiS2 compounds","authors":"Dušica Jovanović, D. Zagorac, B. Matović, A. Zarubica, J. Zagorac","doi":"10.1107/s2052520621008891","DOIUrl":"https://doi.org/10.1107/s2052520621008891","url":null,"abstract":"Recent studies of TiO2/TiS2 nanostructures with various morphologies have been reported, usually showing improved properties with applications from electronics and catalysis to solar cells and medicine. However, there is a limited number of studies on the crystal structures of TiO2/TiS2 compounds with corresponding properties. In this research, relevant crystal structures of TiO1–x\u0000 S\u0000 x\u0000 (x = 0, 0.25, 0.5, 0.75 and 1) solid solutions were investigated using an ab initio method. For each composition, crystal structures adopting anatase, rutile and CdI2 structure type were calculated on LDA-PZ and GGA-PBE levels of theory. Novel phase transitions and predicted structures are presented, and apart from several interesting metastable structures, a very interesting pressure-induced phase transition is found in the TiOS compound. Furthermore, electronic properties were studied through the dependence of semiconducting properties on dopant concentration. The first description of the electronic properties of the mixed TiO1–x\u0000 S\u0000 x\u0000 compounds in crystal form has been presented, followed by a detailed study of the structure–property relationship, which will possibly have numerous industrial and technological applications.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82483375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-22DOI: 10.1107/s2052520621008477
G. Macetti, P. Macchi, A. Genoni
The X-ray restrained wavefunction (XRW) method is a quantum crystallographic technique that allows the calculation of molecular wavefunctions adapted to minimize the difference between computed and reference structure factor amplitudes. The latter result from experimental measurements on crystals or from advanced theoretical calculations with periodic boundary conditions, and are used as external restraints in a traditional least-squares structural refinement. Detailed investigations have shown that the technique is able to reliably capture the effects of the crystal field on the molecular electron density. In a recent application, electron distributions obtained from preliminary X-ray restrained wavefunction calculations have been employed in the framework of frozen density embedding theory to embed excited state computations of well defined subsystems. Inspired by these results, it was decided to test, for the first time, the X-ray restrained extremely localized molecular orbitals (XR-ELMOs) along with the recently developed quantum mechanics/extremely localized molecular orbital multiscale embedding approach. By exploiting XR-ELMOs obtained through XRW calculations that used structure factor amplitudes resulting from periodic ab initio computations, excited state calculations of acrylamide in an environment mimicking the one of the crystal structure were performed. In all these computations, the QM region coincides with the crystal asymmetric unit and the ELMO subsystem consisted of two other acrylamide molecules involved in direct hydrogen bonds with the reference unit. The shifts of the excitation energies with respect to the corresponding gas-phase values were evaluated as a function of different parameters on which the computations with XR-ELMOs depend. For instance, the dependence on the resolution of the sets of structure factors that were used to determine the embedding XR-ELMOs were assessed in particular. The results have shown that the use of XR-ELMOs slightly (but not negligibly) improves the description of excited states compared to the gas-phase ELMOs. Once again, these results demonstrate the efficiency of the XRW approach in incorporating environment effects into the calculated molecular orbitals and, hence, into the corresponding electron densities.
{"title":"X-ray restrained extremely localized molecular orbitals for the embedding of quantum mechanical calculations","authors":"G. Macetti, P. Macchi, A. Genoni","doi":"10.1107/s2052520621008477","DOIUrl":"https://doi.org/10.1107/s2052520621008477","url":null,"abstract":"The X-ray restrained wavefunction (XRW) method is a quantum crystallographic technique that allows the calculation of molecular wavefunctions adapted to minimize the difference between computed and reference structure factor amplitudes. The latter result from experimental measurements on crystals or from advanced theoretical calculations with periodic boundary conditions, and are used as external restraints in a traditional least-squares structural refinement. Detailed investigations have shown that the technique is able to reliably capture the effects of the crystal field on the molecular electron density. In a recent application, electron distributions obtained from preliminary X-ray restrained wavefunction calculations have been employed in the framework of frozen density embedding theory to embed excited state computations of well defined subsystems. Inspired by these results, it was decided to test, for the first time, the X-ray restrained extremely localized molecular orbitals (XR-ELMOs) along with the recently developed quantum mechanics/extremely localized molecular orbital multiscale embedding approach. By exploiting XR-ELMOs obtained through XRW calculations that used structure factor amplitudes resulting from periodic ab initio computations, excited state calculations of acrylamide in an environment mimicking the one of the crystal structure were performed. In all these computations, the QM region coincides with the crystal asymmetric unit and the ELMO subsystem consisted of two other acrylamide molecules involved in direct hydrogen bonds with the reference unit. The shifts of the excitation energies with respect to the corresponding gas-phase values were evaluated as a function of different parameters on which the computations with XR-ELMOs depend. For instance, the dependence on the resolution of the sets of structure factors that were used to determine the embedding XR-ELMOs were assessed in particular. The results have shown that the use of XR-ELMOs slightly (but not negligibly) improves the description of excited states compared to the gas-phase ELMOs. Once again, these results demonstrate the efficiency of the XRW approach in incorporating environment effects into the calculated molecular orbitals and, hence, into the corresponding electron densities.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"109 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79589278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-18DOI: 10.1107/s2052520621008076
Shi Li, Jihe Zhao, Xiao Wang, Li Zhihua, Xuefeng Gui, Jiwen Hu, Shudong Lin, Yuanyuan Tu
A novel type of liquid gating technology has been developed to prepare a polyethylene oxide (PEO) single-crystal film, and the crystal growth was observed via atomic force microscopy. The self-seeding method has been widely used in the preparation of polymer single crystals, but the mechanism through which single polymer crystals are formed via the combination of liquid gating technology and the self-seeding method remains unclear. To elucidate the mechanism of this process, a series of experiments were conducted in which a dilute polymer solution was sprayed onto a mica substrate to form a single-crystal film through liquid gating technology to study the effect of the crystallization time on the morphology of a thiol PEO (mPEO-SH) crystal. Based on this research, it was found that liquid gating helps to prevent twinning during crystal growth. The combination of liquid gating and self-seeding technology thus provides a new strategy for polymer single-crystal growth.
{"title":"Preparation of polyethylene oxide single crystals via liquid gating technology and morphology design strategy","authors":"Shi Li, Jihe Zhao, Xiao Wang, Li Zhihua, Xuefeng Gui, Jiwen Hu, Shudong Lin, Yuanyuan Tu","doi":"10.1107/s2052520621008076","DOIUrl":"https://doi.org/10.1107/s2052520621008076","url":null,"abstract":"A novel type of liquid gating technology has been developed to prepare a polyethylene oxide (PEO) single-crystal film, and the crystal growth was observed via atomic force microscopy. The self-seeding method has been widely used in the preparation of polymer single crystals, but the mechanism through which single polymer crystals are formed via the combination of liquid gating technology and the self-seeding method remains unclear. To elucidate the mechanism of this process, a series of experiments were conducted in which a dilute polymer solution was sprayed onto a mica substrate to form a single-crystal film through liquid gating technology to study the effect of the crystallization time on the morphology of a thiol PEO (mPEO-SH) crystal. Based on this research, it was found that liquid gating helps to prevent twinning during crystal growth. The combination of liquid gating and self-seeding technology thus provides a new strategy for polymer single-crystal growth.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78964117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-18DOI: 10.1107/s2052520621008179
S. Baran, A. Deptuch, A. Hoser, B. Penc, Y. Tyvanchuk, A. Szytuła
The crystal and magnetic structures in R 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx , kx , ½], with kx equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.
{"title":"Crystal and magnetic structures of R\u0000 2Ni1.78In compounds (R = Tb, Ho, Er and Tm)","authors":"S. Baran, A. Deptuch, A. Hoser, B. Penc, Y. Tyvanchuk, A. Szytuła","doi":"10.1107/s2052520621008179","DOIUrl":"https://doi.org/10.1107/s2052520621008179","url":null,"abstract":"The crystal and magnetic structures in R\u0000 2Ni1.78In (R = Ho, Er and Tm) have been studied by neutron diffraction. The compounds crystallize in a tetragonal crystal structure of the Mo2FeB2 type (space group P4/mbm). At low temperatures, the magnetic moments, localized solely on the rare earth atoms, form antiferromagnetic structures described by the propagation vector k = [kx\u0000 , kx\u0000 , ½], with kx\u0000 equal to ¼ for R = Er and Tm or 0.3074 (4) for R = Ho. The magnetic moments are parallel to the c axis for R = Ho or lie within the (001) plane for R = Er and Tm. The obtained magnetic structures are discussed on the basis of symmetry analysis. The rare earth magnetic moments, determined from neutron diffraction data collected at 1.6 K, are 6.5 (1) μB (Er) and 6.09 (4) μB (Tm), while in the incommensurate modulated magnetic structure in Ho2Ni1.78In the amplitude of modulation of the Ho magnetic moment is 7.93 (8) μB. All these values are smaller than those expected for the respective free R\u0000 3+ ions. A symmetry analysis of the magnetic structure in Tb2Ni1.78In is also included, as such information is missing from the original paper [Szytuła, Baran, Hoser, Kalychak, Penc & Tyvanchuk (2013). Acta Phys. Pol. A, 124, 994–997]. In addition, the results of magnetometric measurements are reported for Tm2Ni1.78In. The compound shows antiferromagnetic ordering below the Néel temperature of 4.5 K. Its magnetic properties are found to originate from magnetic moments localized solely on the thulium atoms (the nickel atoms remain non-magnetic in Tm2Ni1.78In). The reduction of rare earth magnetic moments in the ordered state in R\u0000 2Ni1.78In (R = Tb, Ho, Er and Tm) and the change in direction of the moments indicate the influence of the crystalline electric field (CEF) on the stability of the magnetic order in the investigated compounds.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77955411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-18DOI: 10.1107/s205252062100754x
Anna A. Gaydamaka, S. Arkhipov, E. Boldyreva
A new guanine salt hydrate, K+·C5H4N5O−·H2O, was obtained and characterized by single-crystal X-ray diffraction in the temperature range 100 K–300 K and compared with that of the previously documented sodium salt hydrate (2Na+·C5H3N5O2−·7H2O) [Gur & Shimon (2015). Acta Cryst. E71, 281–283; Gaydamaka et al. (2019). CrystEngComm, 21, 4484–4492]. Both sodium and potassium salt hydrates have channels. However, the structure of the channels, the cation coordination, the protonation (and, respectively, the charge) of the guanine anions, as well as the role of water molecules in the crystal structure are different for the two salt hydrates. In the crystal structures of the potassium salt, the guanine anions are linked via hydrogen bonds into quartets that form open cylindrical channels in a honeycomb framework. Water molecules `line the walls' of the channels, whereas the potassium cations fill the intra-channel space. This contrasts with the structure of the sodium salt hydrate in which guanine anions form channels with water molecules filling in the channel space together with sodium cations coordinating them. The 1D anionic assembly generated through numerous hydrogen bonds and cation interactions with guanine anions and water molecules is energetically the most distinctive part of the structure of the potassium salt hydrate. In the case of the guanine sodium salt, the structure contains purely inorganic polymeric fragments – sodium cations coordinated to a water molecule forming a 1D polymeric structure and guanine anions interconnecting these polymers via hydrogen bonds with water molecules. The structural differences account for the difference in the anisotropy of strain on temperature variation for the two salt hydrates: whereas in both structures the values of the bulk thermal expansion coefficients are similar in the two structures and the major expansion is observed along the channel axes, the degree of anisotropy for the K salt is more than four times higher than that for the Na salt.
在100 K - 300 K的温度范围内，获得了一种新的鸟氨酸盐水合物K+·c5h4n50−·H2O，并通过单晶x射线衍射对其进行了表征，并与之前记录的钠盐水合物(2Na+·C5H3N5O2−·7H2O)进行了比较[Gur & Shimon(2015)]。Acta结晶。E71, 281 - 283;Gaydamaka et al.(2019)。[j].计算机工程与应用，2016,33(2):481 - 492。钠盐和钾盐水合物都有通道。然而，两种盐水合物的通道结构、阳离子配位、鸟嘌呤阴离子的质子化(分别为电荷)以及水分子在晶体结构中的作用都不同。在钾盐的晶体结构中，鸟嘌呤阴离子通过氢键连接成四重奏，在蜂窝框架中形成开放的圆柱形通道。水分子排列在通道的壁上，而钾离子则填充在通道内部空间。这与钠盐水合物的结构形成对比，在钠盐水合物中，鸟嘌呤阴离子形成通道，水分子填充在通道空间中，钠离子与之协调。通过与鸟嘌呤阴离子和水分子的大量氢键和阳离子相互作用产生的一维阴离子组装在能量上是水合钾盐结构中最独特的部分。在鸟嘌呤钠盐的情况下，该结构包含纯无机聚合物片段-钠阳离子与水分子配合形成一维聚合物结构，鸟嘌呤阴离子通过氢键与水分子连接这些聚合物。结构差异导致了两种盐水合物应变对温度变化的各向异性差异:两种结构的体热膨胀系数值相似，且膨胀主要沿通道轴方向进行，其中K盐的各向异性程度是Na盐的4倍以上。
{"title":"A new guaninate hydrate K+·C5H4N5O−·H2O: crystal structure from 100 to 300 K in a comparison with 2Na+·C5H3N5O2−·7H2O","authors":"Anna A. Gaydamaka, S. Arkhipov, E. Boldyreva","doi":"10.1107/s205252062100754x","DOIUrl":"https://doi.org/10.1107/s205252062100754x","url":null,"abstract":"A new guanine salt hydrate, K+·C5H4N5O−·H2O, was obtained and characterized by single-crystal X-ray diffraction in the temperature range 100 K–300 K and compared with that of the previously documented sodium salt hydrate (2Na+·C5H3N5O2−·7H2O) [Gur & Shimon (2015). Acta Cryst. E71, 281–283; Gaydamaka et al. (2019). CrystEngComm, 21, 4484–4492]. Both sodium and potassium salt hydrates have channels. However, the structure of the channels, the cation coordination, the protonation (and, respectively, the charge) of the guanine anions, as well as the role of water molecules in the crystal structure are different for the two salt hydrates. In the crystal structures of the potassium salt, the guanine anions are linked via hydrogen bonds into quartets that form open cylindrical channels in a honeycomb framework. Water molecules `line the walls' of the channels, whereas the potassium cations fill the intra-channel space. This contrasts with the structure of the sodium salt hydrate in which guanine anions form channels with water molecules filling in the channel space together with sodium cations coordinating them. The 1D anionic assembly generated through numerous hydrogen bonds and cation interactions with guanine anions and water molecules is energetically the most distinctive part of the structure of the potassium salt hydrate. In the case of the guanine sodium salt, the structure contains purely inorganic polymeric fragments – sodium cations coordinated to a water molecule forming a 1D polymeric structure and guanine anions interconnecting these polymers via hydrogen bonds with water molecules. The structural differences account for the difference in the anisotropy of strain on temperature variation for the two salt hydrates: whereas in both structures the values of the bulk thermal expansion coefficients are similar in the two structures and the major expansion is observed along the channel axes, the degree of anisotropy for the K salt is more than four times higher than that for the Na salt.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85125510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-17DOI: 10.1107/s2052520621007988
R. Sibille, T. Mazet, L. Diop, M. François
The structure of M 2(OH)2(bpdc) (bpdc = biphenyl dicarboxylate, C14H8O4) is distinct from that of the isoreticular compounds M 2(OH)2(bdc) (bdc = benzene dicarboxylate, C8H4O4) (M = Mn, Fe), in the sense that no disorder of the bpdc molecules from one layer to the other needs to be considered. The global symmetry is lower in the bpdc compounds (P 1) than in the bdc compounds (C2/m). Both Mn2(OH)2(bpdc) and Fe2(OH)2(bpdc) order magnetically at 36.8 and 46.5 K, respectively, and can be considered as uncompensated antiferromagnets, whereas Mn2(OH)2(bdc) (Néel temperature T N = 38.5 K) and Fe2(OH)2(bdc) (T N = 66 K) are compensated antiferromagnets.
{"title":"Crystal structure and magnetic properties of the layered hybrid organic–inorganic compounds M\u0000 2(OH)2(C14H8O4) (M = Mn, Fe)","authors":"R. Sibille, T. Mazet, L. Diop, M. François","doi":"10.1107/s2052520621007988","DOIUrl":"https://doi.org/10.1107/s2052520621007988","url":null,"abstract":"The structure of M\u0000 2(OH)2(bpdc) (bpdc = biphenyl dicarboxylate, C14H8O4) is distinct from that of the isoreticular compounds M\u0000 2(OH)2(bdc) (bdc = benzene dicarboxylate, C8H4O4) (M = Mn, Fe), in the sense that no disorder of the bpdc molecules from one layer to the other needs to be considered. The global symmetry is lower in the bpdc compounds (P\u0000 1) than in the bdc compounds (C2/m). Both Mn2(OH)2(bpdc) and Fe2(OH)2(bpdc) order magnetically at 36.8 and 46.5 K, respectively, and can be considered as uncompensated antiferromagnets, whereas Mn2(OH)2(bdc) (Néel temperature T\u0000 N = 38.5 K) and Fe2(OH)2(bdc) (T\u0000 N = 66 K) are compensated antiferromagnets.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"62 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83417621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-16DOI: 10.1107/S2052520621008027
Zhiping Luo
The crystal structure of γ-alumina was revealed by electron crystallography and its transformation mechanism from boehmite is proposed.
利用电子晶体学研究了γ-氧化铝的晶体结构，并提出了其由薄水铝石转变成γ-氧化铝的机理。
{"title":"Structure of boehmite-derived γ-alumina and its transformation mechanism revealed by electron crystallography","authors":"Zhiping Luo","doi":"10.1107/S2052520621008027","DOIUrl":"https://doi.org/10.1107/S2052520621008027","url":null,"abstract":"The crystal structure of γ-alumina was revealed by electron crystallography and its transformation mechanism from boehmite is proposed.","PeriodicalId":7080,"journal":{"name":"Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials","volume":"47 1","pages":"772 - 784"},"PeriodicalIF":0.0,"publicationDate":"2021-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77411058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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