Pub Date : 2017-12-01DOI: 10.1107/S2052520617015888
L. Battezzati
Intermetallics are solid-state compounds exhibiting metallic bonding, defined stoichiometry and ordered crystal structure. It is now a century since it was recognized in an early book (Giua & Lollini Giua, 1918), written by Michele Giua, Professor of Industrial Chemistry at Turin University together with his wife Clara Lollini Giua, that numerous compounds could form. Many more were discovered in the following decades. A few gained increasing industrial interest, e.g. aluminides, but it was only in 1993 that a dedicated journal, Intermetallics, was founded by the late Robert Cahn. Now, here comes the book Intermetallics with subtitle Structures, Properties and Statistics by Walter Steurer and Julia Dshemuchadse which sets a new paradigm in the topic by analyzing the structure and classifying the tens of thousands intermetallics known to date. The book is divided in two parts: Concepts and Statistics are the content of Part I and Structure and Properties of Part II. The text is full of information filling more than 500 pages. It has an extensive literature section as well an index of chemical formulae. A useful list of abbreviations and a glossary are provided. The linguistic approach is rigorous in terminology and in making reference to theories, methods and rules. Chapter 1 gives the basic terminology concerning symmetry, lattices, atomic environment types. It is clear and well organized. I would suggest it to students of materials science courses to learn definitions properly. The second chapter summarizes the factors governing structure and stability of intermetallics with emphasis mainly on quantum chemistry. The quantum chemistry methods employed in the literature are mentioned with a short description of up to one page. For the reader not experienced in this topic, this section is of limited usefulness considering also the absence of illustrations. It is understood a more lengthy treatment would have diverted the text from its main objectives. The authors, however, direct the reader to the relevant literature for all methods. Being perhaps biased by my thermodynamic background, I felt the stability issue could have been tackled also by mentioning the methods employed to evaluate the Gibbs free energy of intermetallics, especially because the calculation of this quantity is an expanding topic for those performing phase diagram calculations including the calculation of the enthalpy of formation from first principles. The description of tilings in Chapter 3 is detailed, though concise, with good examples and images. This represents the basis for building up the structure of complex intermetallics through an accurate description of polyhedra and packings. The next step is the treatment of n-dimensional spaces to represent the structure of both complex periodic and aperiodic compounds in Chapter 4. The following Chapter 5, is the most innovative one dealing with a statistical analysis of the occurrence of intermetallics in binary (the largest nu
{"title":"Intermetallics. Structures, Properties, and Statistics. By Walter Steurer and Julia Dshemuchadse. Oxford University Press, 2016, Hardcover, Pp. 592. Price GBP 85.00. ISBN 9780198714552","authors":"L. Battezzati","doi":"10.1107/S2052520617015888","DOIUrl":"https://doi.org/10.1107/S2052520617015888","url":null,"abstract":"Intermetallics are solid-state compounds exhibiting metallic bonding, defined stoichiometry and ordered crystal structure. It is now a century since it was recognized in an early book (Giua & Lollini Giua, 1918), written by Michele Giua, Professor of Industrial Chemistry at Turin University together with his wife Clara Lollini Giua, that numerous compounds could form. Many more were discovered in the following decades. A few gained increasing industrial interest, e.g. aluminides, but it was only in 1993 that a dedicated journal, Intermetallics, was founded by the late Robert Cahn. Now, here comes the book Intermetallics with subtitle Structures, Properties and Statistics by Walter Steurer and Julia Dshemuchadse which sets a new paradigm in the topic by analyzing the structure and classifying the tens of thousands intermetallics known to date. The book is divided in two parts: Concepts and Statistics are the content of Part I and Structure and Properties of Part II. The text is full of information filling more than 500 pages. It has an extensive literature section as well an index of chemical formulae. A useful list of abbreviations and a glossary are provided. The linguistic approach is rigorous in terminology and in making reference to theories, methods and rules. Chapter 1 gives the basic terminology concerning symmetry, lattices, atomic environment types. It is clear and well organized. I would suggest it to students of materials science courses to learn definitions properly. The second chapter summarizes the factors governing structure and stability of intermetallics with emphasis mainly on quantum chemistry. The quantum chemistry methods employed in the literature are mentioned with a short description of up to one page. For the reader not experienced in this topic, this section is of limited usefulness considering also the absence of illustrations. It is understood a more lengthy treatment would have diverted the text from its main objectives. The authors, however, direct the reader to the relevant literature for all methods. Being perhaps biased by my thermodynamic background, I felt the stability issue could have been tackled also by mentioning the methods employed to evaluate the Gibbs free energy of intermetallics, especially because the calculation of this quantity is an expanding topic for those performing phase diagram calculations including the calculation of the enthalpy of formation from first principles. The description of tilings in Chapter 3 is detailed, though concise, with good examples and images. This represents the basis for building up the structure of complex intermetallics through an accurate description of polyhedra and packings. The next step is the treatment of n-dimensional spaces to represent the structure of both complex periodic and aperiodic compounds in Chapter 4. The following Chapter 5, is the most innovative one dealing with a statistical analysis of the occurrence of intermetallics in binary (the largest nu","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"1 1","pages":"1194-1195"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90386754","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 : 2017-12-01DOI: 10.1107/S2052520617013270
Tsunetomo Yamada, H. Takakura, M. Boissieu, A. Tsai
Atomic structures of ternary icosahedral (i) Yb–Cd–Mg quasicrystals (QCs) with five different Mg contents up to 46.4 at.% and a corresponding 1/1 approximant (AP), which has a composition of Yb13.3Cd70.3Mg16.5, have been analysed by single-crystal X-ray diffraction. The structures of the iQCs were found to be isostructural to the parent i-YbCd5.7, which consists of a so-called Tsai-type rhombic triacontahedron (RTH) cluster and double Friauf polyhedron, and that of the 1/1 AP was found to be isostructural to YbCd6, which is described by a body-centred packing of the same type of RTH cluster. In the iQCs, it was found that there are three types of Cd/Mg occupation, namely, Cd preferential site, Mg preferential site and Cd/Mg mixed site, and the occupation probabilities of Mg atoms at the Mg preferential site show a saturation behaviour around the Mg content of 20 at.%. This selective Mg occupation is identified as a cause of the non-linear increase in the icosahedral lattice constant with increasing Mg content. The 1/1 AP has a similar selective Mg occupation to that of the iQCs in terms of the shell structures of the Tsai-type RTH cluster. In both iQCs and the 1/1 AP, the Mg preferential sites have a smaller number of Yb atoms among their coordination numbers. Moreover, short-range order (s.r.o.) diffuse scattering was observed on the diffraction patterns of the iQCs at the positions corresponding to a face-centred-type (F-type) icosahedral superlattice. The F-type s.r.o. was found to result from the Mg substitution.
{"title":"Atomic structures of ternary Yb–Cd–Mg icosahedral quasicrystals and a 1/1 approximant","authors":"Tsunetomo Yamada, H. Takakura, M. Boissieu, A. Tsai","doi":"10.1107/S2052520617013270","DOIUrl":"https://doi.org/10.1107/S2052520617013270","url":null,"abstract":"Atomic structures of ternary icosahedral (i) Yb–Cd–Mg quasicrystals (QCs) with five different Mg contents up to 46.4 at.% and a corresponding 1/1 approximant (AP), which has a composition of Yb13.3Cd70.3Mg16.5, have been analysed by single-crystal X-ray diffraction. The structures of the iQCs were found to be isostructural to the parent i-YbCd5.7, which consists of a so-called Tsai-type rhombic triacontahedron (RTH) cluster and double Friauf polyhedron, and that of the 1/1 AP was found to be isostructural to YbCd6, which is described by a body-centred packing of the same type of RTH cluster. In the iQCs, it was found that there are three types of Cd/Mg occupation, namely, Cd preferential site, Mg preferential site and Cd/Mg mixed site, and the occupation probabilities of Mg atoms at the Mg preferential site show a saturation behaviour around the Mg content of 20 at.%. This selective Mg occupation is identified as a cause of the non-linear increase in the icosahedral lattice constant with increasing Mg content. The 1/1 AP has a similar selective Mg occupation to that of the iQCs in terms of the shell structures of the Tsai-type RTH cluster. In both iQCs and the 1/1 AP, the Mg preferential sites have a smaller number of Yb atoms among their coordination numbers. Moreover, short-range order (s.r.o.) diffuse scattering was observed on the diffraction patterns of the iQCs at the positions corresponding to a face-centred-type (F-type) icosahedral superlattice. The F-type s.r.o. was found to result from the Mg substitution.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"75 1","pages":"1125-1141"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83812708","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 : 2017-12-01DOI: 10.1107/S2052520617015591
Khai‐Nghi Truong, C. Merkens, M. Meven, Björn Faßbänder, R. Dronskowski, U. Englert
Single-crystal neutron diffraction experiments at 100 and 2.5 K have been performed to determine the structure of 3-(pyridin-4-yl)pentane-2,4-dione (HacacPy) with respect to its protonation pattern and to monitor a low-temperature phase transition. Solid HacacPy exists as the enol tautomer with a short intramolecular hydrogen bond. At 100 K, its donor···acceptor distance is 2.450 (8) A and the compound adopts space group C2/c, with the N and para-C atoms of the pyridyl ring and the central C of the acetylacetone substituent on the twofold crystallographic axis. As a consequence of the axial symmetry, the bridging hydrogen is disordered over two symmetrically equivalent positions, and the carbon–oxygen bond distances adopt intermediate values between single and double bonds. Upon cooling, a structural phase transition to the t2 subgroup Pbar 1 occurs; the resulting twins show an ordered acetylacetone moiety. The phase transition is fully reversible but associated with an appreciable hysteresis in the large single crystal under study: transition to the low-temperature phase requires several hours at 2.5 K and heating to 80 K is required to revert the transformation. No significant hysteresis is observed in a powder sample, in agreement with the second-order nature of the phase transition.
{"title":"Phase transition and proton ordering at 50 K in 3-(pyridin-4-yl)pentane-2,4-dione","authors":"Khai‐Nghi Truong, C. Merkens, M. Meven, Björn Faßbänder, R. Dronskowski, U. Englert","doi":"10.1107/S2052520617015591","DOIUrl":"https://doi.org/10.1107/S2052520617015591","url":null,"abstract":"Single-crystal neutron diffraction experiments at 100 and 2.5 K have been performed to determine the structure of 3-(pyridin-4-yl)pentane-2,4-dione (HacacPy) with respect to its protonation pattern and to monitor a low-temperature phase transition. Solid HacacPy exists as the enol tautomer with a short intramolecular hydrogen bond. At 100 K, its donor···acceptor distance is 2.450 (8) A and the compound adopts space group C2/c, with the N and para-C atoms of the pyridyl ring and the central C of the acetylacetone substituent on the twofold crystallographic axis. As a consequence of the axial symmetry, the bridging hydrogen is disordered over two symmetrically equivalent positions, and the carbon–oxygen bond distances adopt intermediate values between single and double bonds. Upon cooling, a structural phase transition to the t2 subgroup Pbar 1 occurs; the resulting twins show an ordered acetylacetone moiety. The phase transition is fully reversible but associated with an appreciable hysteresis in the large single crystal under study: transition to the low-temperature phase requires several hours at 2.5 K and heating to 80 K is required to revert the transformation. No significant hysteresis is observed in a powder sample, in agreement with the second-order nature of the phase transition.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"151 1","pages":"1172-1178"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79517438","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 : 2017-12-01DOI: 10.1107/S2052520617012422
A. Udovenko, E. I. Pogoreltsev, Yu.V. Marchenko, N. Laptash
Single crystals of (NH4)3VOF5 and (NH4)3VO2F4 were obtained from aqueous fluoride solutions and phase transitions in these compounds were investigated using X-ray diffraction, differential scanning microcalorimetry (DSM) and vibrational spectroscopy. The room-temperature (RT) phases of these compounds belong to orthorhombic symmetry [Immm and I222, Z = 6, for (NH4)3VOF5 and (NH4)3VO2F4, respectively] with similar unit-cell parameters and two independent vanadium atoms. Above RT [at 350 and 440 K for (NH4)3VOF5 and (NH4)3VO2F4, respectively], the compounds undergo reversible phase transitions into high-symmetry dynamically disordered elpasolite-like (Fm{bar 3}m, Z = 4) structures with six and 12 spatial orientations of the vanadium octahedron for (NH4)3VOF5 and (NH4)3VO2F4, respectively. The ligand atoms are distributed in a mixed (split) position of 24e + 96j, one of the ammonium groups is disordered on the tetrahedron 32f site, but another one forms eight spatial orientations due to disorder of its hydrogen atoms in the 96j position. DSM and spectroscopic data enable the phase transition from high temperature to room temperature to be connected with the transition from isotropic orientations of the octahedron to its two different dynamic states.
采用x射线衍射、差示扫描微量热法(DSM)和振动光谱法研究了氟化物水溶液中(NH4)3VOF5和(NH4)3VO2F4单晶的相变。这些化合物的室温(RT)相属于正交对称[Immm和I222, Z = 6，分别为(NH4)3VOF5和(NH4)3VO2F4]，具有相似的单位胞参数和两个独立的钒原子。在RT以上[(NH4)3VOF5和(NH4)3VO2F4分别在350和440 K下]，(NH4)3VOF5和(NH4)3VO2F4分别发生可逆相变，形成具有钒八面体6个和12个空间取向的高对称性动态无序类斜长石(Fm{bar 3}m, Z = 4)结构。配体原子以24e + 96j的混合(分裂)位置分布，其中一个铵基在四面体32f位上无序，而另一个铵基由于其96j位氢原子的无序而形成八个空间取向。DSM和光谱数据表明，从高温到室温的相变与八面体从各向同性取向到两种不同动态状态的转变有关。
{"title":"Orientational disorder and phase transitions in ammonium oxofluorovanadates, (NH4)3VOF5 and (NH4)3VO2F4","authors":"A. Udovenko, E. I. Pogoreltsev, Yu.V. Marchenko, N. Laptash","doi":"10.1107/S2052520617012422","DOIUrl":"https://doi.org/10.1107/S2052520617012422","url":null,"abstract":"Single crystals of (NH4)3VOF5 and (NH4)3VO2F4 were obtained from aqueous fluoride solutions and phase transitions in these compounds were investigated using X-ray diffraction, differential scanning microcalorimetry (DSM) and vibrational spectroscopy. The room-temperature (RT) phases of these compounds belong to orthorhombic symmetry [Immm and I222, Z = 6, for (NH4)3VOF5 and (NH4)3VO2F4, respectively] with similar unit-cell parameters and two independent vanadium atoms. Above RT [at 350 and 440 K for (NH4)3VOF5 and (NH4)3VO2F4, respectively], the compounds undergo reversible phase transitions into high-symmetry dynamically disordered elpasolite-like (Fm{bar 3}m, Z = 4) structures with six and 12 spatial orientations of the vanadium octahedron for (NH4)3VOF5 and (NH4)3VO2F4, respectively. The ligand atoms are distributed in a mixed (split) position of 24e + 96j, one of the ammonium groups is disordered on the tetrahedron 32f site, but another one forms eight spatial orientations due to disorder of its hydrogen atoms in the 96j position. DSM and spectroscopic data enable the phase transition from high temperature to room temperature to be connected with the transition from isotropic orientations of the octahedron to its two different dynamic states.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"17 1","pages":"1085-1094"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82477835","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 : 2017-12-01DOI: 10.1107/S2052520617012872
A. Bhakar, Adityanarayan H. Pandey, M. Singh, A. Upadhyay, A. Sinha, S. M. Gupta, T. Ganguli, S. Rai
The synchrotron powder X-ray diffraction (XRD) and subsequent detailed Rietveld analysis of lead magnesium niobate (PMN) samples were performed to study the microstructural properties of polar nanoregions (PNRs) of the R3m phase. PMN samples were synthesized under different sample processing conditions. The line profile broadening analysis of room-temperature synchrotron powder XRD patterns was performed using the multi-phase Rietveld refinement method for isotropic microstructural evaluation of different PMN samples. The two phases of perovskite PMN considered in the Rietveld refinement approach for satisfactorily fitting the XRD patterns are the paraelectric cubic phase (Pm m) and the local rhombohedral phase (R3m) which corresponds to the PNRs. It is observed that the contributions of the Gaussian component of size broadening of the polar rhombohedral phase (R3m) and the Lorentzian component of strain broadening of the paraelectric cubic phase (Pm m) are apposite for satisfactory Rietveld refinement of the synchrotron XRD data for all PMN samples. The volume-average crystallite size of PNRs (R3m phase) is almost invariant (approximately 12 nm) with increasing processing temperature while their weight percentage increases. The values of the apparent microstrain in the paraelectric cubic phase (Pm m) are larger for hot-pressed samples.
{"title":"Effect of processing parameters on microstructural properties of lead magnesium niobates","authors":"A. Bhakar, Adityanarayan H. Pandey, M. Singh, A. Upadhyay, A. Sinha, S. M. Gupta, T. Ganguli, S. Rai","doi":"10.1107/S2052520617012872","DOIUrl":"https://doi.org/10.1107/S2052520617012872","url":null,"abstract":"The synchrotron powder X-ray diffraction (XRD) and subsequent detailed Rietveld analysis of lead magnesium niobate (PMN) samples were performed to study the microstructural properties of polar nanoregions (PNRs) of the R3m phase. PMN samples were synthesized under different sample processing conditions. The line profile broadening analysis of room-temperature synchrotron powder XRD patterns was performed using the multi-phase Rietveld refinement method for isotropic microstructural evaluation of different PMN samples. The two phases of perovskite PMN considered in the Rietveld refinement approach for satisfactorily fitting the XRD patterns are the paraelectric cubic phase (Pm m) and the local rhombohedral phase (R3m) which corresponds to the PNRs. It is observed that the contributions of the Gaussian component of size broadening of the polar rhombohedral phase (R3m) and the Lorentzian component of strain broadening of the paraelectric cubic phase (Pm m) are apposite for satisfactory Rietveld refinement of the synchrotron XRD data for all PMN samples. The volume-average crystallite size of PNRs (R3m phase) is almost invariant (approximately 12 nm) with increasing processing temperature while their weight percentage increases. The values of the apparent microstrain in the paraelectric cubic phase (Pm m) are larger for hot-pressed samples.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"45 1","pages":"1095-1104"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90889793","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 : 2017-12-01DOI: 10.1107/S205252061701441X
C. Bull, N. Funnell, C. Pulham, W. G. Marshall, D. Allan
The high-pressure structural behaviour of phosphoric acid is described. A compression study of the monoclinic phase, using neutron powder diffraction and X-ray single-crystal diffraction, shows that it converts to a previously unobserved orthorhombic phase on decompression. Compression of this new phase is reported up to 6.3 GPa. The orthorhombic phase is found to be more efficiently packed, with reduced void space, resulting in a larger bulk modulus. Molecule–molecule interaction energies reveal a more extensive network of increased attractive forces in the orthorhombic form relative to the monoclinic form, suggesting greater thermodynamic stability.
{"title":"A new high‐pressure polymorph of phosphoric acid","authors":"C. Bull, N. Funnell, C. Pulham, W. G. Marshall, D. Allan","doi":"10.1107/S205252061701441X","DOIUrl":"https://doi.org/10.1107/S205252061701441X","url":null,"abstract":"The high-pressure structural behaviour of phosphoric acid is described. A compression study of the monoclinic phase, using neutron powder diffraction and X-ray single-crystal diffraction, shows that it converts to a previously unobserved orthorhombic phase on decompression. Compression of this new phase is reported up to 6.3 GPa. The orthorhombic phase is found to be more efficiently packed, with reduced void space, resulting in a larger bulk modulus. Molecule–molecule interaction energies reveal a more extensive network of increased attractive forces in the orthorhombic form relative to the monoclinic form, suggesting greater thermodynamic stability.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"59 1","pages":"1068-1074"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80539401","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 : 2017-12-01DOI: 10.1107/S205252061701575X
T. Guerfi
It may be argued that the remarkable properties of the high-temperature superconducting cuprates such as the insulator–metal transition (IMT) and the metal–superconductor transition (MST) originate from competition and interplay between the interlayer ionic interaction and the intralayer covalent bonds in these materials. It is proposed here that the microscopic order parameter is the local field estimated from the ionic polarization at the sub-unit cell level, and it is demonstrated that it shows a strong temperature as well as chemical doping dependence. The out-of-plane ionicity induces an interlayer electron transfer that reduces the ionicity of the layers and leads to IMT, while the in-plane covalency induces in-plane intersite hole transfer that increases the out-of-plane ionicity. It is suggested that this competition leads to a local field catastrophe at a critical temperature Tc that drives the compound to MST. The asymmetry of the free charge carrier density breaks locally the mirror reflection symmetry of the order parameter, leading to a pairing between the real current and the polarization current.
{"title":"Out-of-plane ionicity versus in-plane covalency interplay in high-Tc cuprates","authors":"T. Guerfi","doi":"10.1107/S205252061701575X","DOIUrl":"https://doi.org/10.1107/S205252061701575X","url":null,"abstract":"It may be argued that the remarkable properties of the high-temperature superconducting cuprates such as the insulator–metal transition (IMT) and the metal–superconductor transition (MST) originate from competition and interplay between the interlayer ionic interaction and the intralayer covalent bonds in these materials. It is proposed here that the microscopic order parameter is the local field estimated from the ionic polarization at the sub-unit cell level, and it is demonstrated that it shows a strong temperature as well as chemical doping dependence. The out-of-plane ionicity induces an interlayer electron transfer that reduces the ionicity of the layers and leads to IMT, while the in-plane covalency induces in-plane intersite hole transfer that increases the out-of-plane ionicity. It is suggested that this competition leads to a local field catastrophe at a critical temperature Tc that drives the compound to MST. The asymmetry of the free charge carrier density breaks locally the mirror reflection symmetry of the order parameter, leading to a pairing between the real current and the polarization current.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"1 1","pages":"1164-1171"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83993447","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 : 2017-12-01DOI: 10.1107/S2052520617016018
G. Koster
In his book Intelligent Materials and Structures, Abramovich attempts to give a complete overview of coupled effects found in materials or composites which can be used to design a system that responds intelligently to its environment. By definition this ‘field’ is served from different disciplines such as micro-engineering sciences, electrical engineering and materials sciences, and the author is seemingly comfortable in communicating to all. Although coupled effects could in principle comprise many different materials properties (piezo, electrical resistance etc. etc.) responsive to a vast range of external stimuli (electrical, mechanical, chemical etc.), the book is ultimately restricted to mechanical responses, such as piezoelectrical, shape memory, electrorheological and magnetorheological and electroand magnetostrictive responses. All topics are broadly covered by a brief general description of the effect, a few examples of applications and the governing coupling constants, to an in-depth discussion of the leading phenomenological models. Sometimes, in places the reader might be overwhelmed by the amount numberof mathematical equations; however, the author has made an attempt to move some of the definitions to appendices in order to maintain readability. Figures are mostly appealing and illustrative, in particular when supporting the applications. Overall, the text seems well prepared and the general appearance is appealing. Depending on their background, readers from micro-engineering can use the book as a thorough introduction as well as a reference text. Scientists who lay an emphasis on the application as well as development of continuum models for materials may find the book really useful. For these sections, the readers should be comfortable with tensor and vector calculus and solving partial differential equations. Researchers from the basic sciences connected to microstructure and first-principle modelling are not so well served by this book in terms of the theoretical aspects but possibly may find it a useful resource for literature on applications. The first chapter starts with a very general introduction to the field of smart materials, positioning the topics covered in the book. Also, for the four types of materials a literature review is given, categorized by application. For those readers in need of broad access to all or some of the materials systems discussed, this chapter should be sufficient. Subsequently, five chapters are dedicated to a detailed discussion of the previously mentioned effects, all having a more or less similar outline, from the basic applications and equations to a discussion on the models with a phenomenological basis using continuum equations. In particular, piezoelectricity is given a broad podium with discussions on details of this material class (PZT) in various mechanical configurations. If a reader is mostly interested in this particular property, he or she might be better served by a more dedicated
{"title":"Intelligent Materials and Structures. By Haim Abramovich. De Gruyter, 2016, Paperback, Pp. VIII+378. Price EUR 69.95, USD 98.00, GBP 52.99. ISBN 978-3-11-033801-0","authors":"G. Koster","doi":"10.1107/S2052520617016018","DOIUrl":"https://doi.org/10.1107/S2052520617016018","url":null,"abstract":"In his book Intelligent Materials and Structures, Abramovich attempts to give a complete overview of coupled effects found in materials or composites which can be used to design a system that responds intelligently to its environment. By definition this ‘field’ is served from different disciplines such as micro-engineering sciences, electrical engineering and materials sciences, and the author is seemingly comfortable in communicating to all. Although coupled effects could in principle comprise many different materials properties (piezo, electrical resistance etc. etc.) responsive to a vast range of external stimuli (electrical, mechanical, chemical etc.), the book is ultimately restricted to mechanical responses, such as piezoelectrical, shape memory, electrorheological and magnetorheological and electroand magnetostrictive responses. All topics are broadly covered by a brief general description of the effect, a few examples of applications and the governing coupling constants, to an in-depth discussion of the leading phenomenological models. Sometimes, in places the reader might be overwhelmed by the amount numberof mathematical equations; however, the author has made an attempt to move some of the definitions to appendices in order to maintain readability. Figures are mostly appealing and illustrative, in particular when supporting the applications. Overall, the text seems well prepared and the general appearance is appealing. Depending on their background, readers from micro-engineering can use the book as a thorough introduction as well as a reference text. Scientists who lay an emphasis on the application as well as development of continuum models for materials may find the book really useful. For these sections, the readers should be comfortable with tensor and vector calculus and solving partial differential equations. Researchers from the basic sciences connected to microstructure and first-principle modelling are not so well served by this book in terms of the theoretical aspects but possibly may find it a useful resource for literature on applications. The first chapter starts with a very general introduction to the field of smart materials, positioning the topics covered in the book. Also, for the four types of materials a literature review is given, categorized by application. For those readers in need of broad access to all or some of the materials systems discussed, this chapter should be sufficient. Subsequently, five chapters are dedicated to a detailed discussion of the previously mentioned effects, all having a more or less similar outline, from the basic applications and equations to a discussion on the models with a phenomenological basis using continuum equations. In particular, piezoelectricity is given a broad podium with discussions on details of this material class (PZT) in various mechanical configurations. If a reader is mostly interested in this particular property, he or she might be better served by a more dedicated","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"28 1","pages":"1196-1197"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84920244","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 : 2017-12-01DOI: 10.1107/S2052520617012847
E. Selezneva, I. Makarova, I. Malyshkina, N. D. Gavrilova, V. Grebenev, V. K. Novik, V. Komornikov
Investigations of new single crystals grown in the K3H(SO4)2–(NH4)3H(SO4)2–H2O system from solutions with different K:NH4 concentration ratios have been carried out. Based on the X-ray diffraction data, the atomic structure of the crystals was determined at room temperature taking H atoms into account. It has been determined that [K0.43(NH4)0.57]3H(SO4)2 crystals are trigonal at ambient conditions such as the superprotonic phase of (NH4)3H(SO4)2 at high temperature. A distribution of the K and N atoms in the crystal was modelled on the basis of the refined occupancies of K/N positions. Studies of dielectric properties over the temperature range 223–353 K revealed high values of conductivity of the crystals comparable with the conductivity of known superprotonic compounds at high temperatures, and an anomaly corresponding to a transition to the phase with low conductivity upon cooling.
{"title":"New superprotonic crystals with dynamically disordered hydrogen bonds: cation replacements as the alternative to temperature increase","authors":"E. Selezneva, I. Makarova, I. Malyshkina, N. D. Gavrilova, V. Grebenev, V. K. Novik, V. Komornikov","doi":"10.1107/S2052520617012847","DOIUrl":"https://doi.org/10.1107/S2052520617012847","url":null,"abstract":"Investigations of new single crystals grown in the K3H(SO4)2–(NH4)3H(SO4)2–H2O system from solutions with different K:NH4 concentration ratios have been carried out. Based on the X-ray diffraction data, the atomic structure of the crystals was determined at room temperature taking H atoms into account. It has been determined that [K0.43(NH4)0.57]3H(SO4)2 crystals are trigonal at ambient conditions such as the superprotonic phase of (NH4)3H(SO4)2 at high temperature. A distribution of the K and N atoms in the crystal was modelled on the basis of the refined occupancies of K/N positions. Studies of dielectric properties over the temperature range 223–353 K revealed high values of conductivity of the crystals comparable with the conductivity of known superprotonic compounds at high temperatures, and an anomaly corresponding to a transition to the phase with low conductivity upon cooling.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"24 2 1","pages":"1105-1113"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90420916","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 : 2017-12-01DOI: 10.1107/S2052520617015657
Ian B. Hutchison, C. Bull, W. G. Marshall, S. Parsons, A. Urquhart, I. Oswald
This study details the structural characterisation of glycolide-h4 as a function of pressure to 6 GPa using neutron powder diffraction on the PEARL instrument at ISIS Neutron and Muon source. Glycolide-h4, rather than its deuterated isotopologue, was used in this study due to the difficulty of deuteration. The low-background afforded by Zirconia-Toughened Alumina (ZTA) anvils nevertheless enabled the collection of data suitable for structural analysis to be obtained to a pressure of 5 GPa. Glycolide-h4 undergoes a reconstructive phase transition at 0.15 GPa to a previously identified, form-II, which is stable to 6 GPa.
{"title":"Compression of glycolide-h4 to 6 GPa","authors":"Ian B. Hutchison, C. Bull, W. G. Marshall, S. Parsons, A. Urquhart, I. Oswald","doi":"10.1107/S2052520617015657","DOIUrl":"https://doi.org/10.1107/S2052520617015657","url":null,"abstract":"This study details the structural characterisation of glycolide-h4 as a function of pressure to 6 GPa using neutron powder diffraction on the PEARL instrument at ISIS Neutron and Muon source. Glycolide-h4, rather than its deuterated isotopologue, was used in this study due to the difficulty of deuteration. The low-background afforded by Zirconia-Toughened Alumina (ZTA) anvils nevertheless enabled the collection of data suitable for structural analysis to be obtained to a pressure of 5 GPa. Glycolide-h4 undergoes a reconstructive phase transition at 0.15 GPa to a previously identified, form-II, which is stable to 6 GPa.","PeriodicalId":6887,"journal":{"name":"Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry","volume":"173 1","pages":"1151-1157"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84009416","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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