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The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. The list includes various papers on topics such as molecular packing characteristics, crystal structures, photocatalytic activity, crystal growth, and more. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document also mentions approved training courses offered by the society. [Extracted from the article]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. It includes a list of papers featured in the issue, covering topics such as photoluminescent detection, phosphors for light-emitting diodes, crystal derivatives, piezoelectric materials, graphene growth, and nanocrystal synthesis. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document also mentions approved training courses offered by the society. [Extracted from the article]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. The list includes various papers on topics such as hybrid materials, growth of single-crystalline particles, high-pressure phase transitions, coordination polymers, and optical properties of crystals. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document also mentions professional recognition and development opportunities for scientists. [Extracted from the article]

The high pressure structure of α-oxalic acid di-hydrate shows a prototypical behaviour of acid to base proton transfer reaction. The solid state transformation has been characterized by neutron and X-ray diffraction as well as by quantum chemical calculations with periodic boundary conditions. The two resonant configurations playing the most important role in the hydrogen bond mechanism, i.e.a neutral and a charge transfer configuration, are interchanged by modifying the pressure on the system. A different behaviour is predicted for the less common β form, despite an apparently similar packing motif. Implications for the characterization of hydrogen bonds in the solid state are discussed as well as the possibility of estimating internal energy variations from experimental measurements. [ABSTRACT FROM AUTHOR]

Solvent induced single-crystal-to-single-crystal transformation has been demonstrated indicating the dynamic behavior of one dimensional arrays obtained from a self-assembled new synthetic cyclic peptide. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Na+ concentration on the crystalline phase, morphology, and content of vaterite in a system with different Ca2+ and CO32− ratios using steamed ammonia liquid waste as the calcium source was investigated, and the effect of Na+ on the yield of vaterite was studied systematically for the first time. The obtained products were characterized by powder X-ray diffraction (XRPD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, laser particle size analysis (LPSA), and so on. The results show that the variation of Na+ concentration in different Ca2+ and CO32− ratio systems has an effect on the particle size, morphology, content, and CaCO3 yield of vaterite. Thermogravimetric (TG) analysis indicates that Na+ is involved in forming CaCO3 but does not enter the interior of the vaterite crystals. Mechanistic analysis shows that changes in Na+ concentration can alter the initial pH of the reaction system and the conductivity of the solution, thus changing the processes such as early nucleation and crystal growth of vaterite as well as inhibiting the vaterite phase transition, which determines the particle size of the vaterite obtained. This study reveals to a certain extent the influence of Na+ on the early nucleation and crystal growth of vaterite and provides theoretical support for the realization of large-scale industrial production of vaterite. [ABSTRACT FROM AUTHOR]

Molecular-based dielectric switching materials are special crystal–crystal structure phase transition materials, and play an important role in multifunctional materials and other fields. In this paper, a trivalent cyclic amine is used as the building unit to successfully prepare a molecular crystal material, 1,4,7-triazacyclononane trihydrochloride, 1, with abundant hydrogen bonds and high temperature dielectric switching properties, and its IR, TGA, DSC, VT-PXRD (variable-temperature PXRD), VT-structures, and T–ε′ (temperature dependence of the real part of the dielectric constant) are characterized and analyzed. The space group of 1 is P21/n at 298 K and R3¯m at 403 K. Two endothermic peaks appeared near 369 K and 380 K and one exothermic peak appeared near 363.5 K in the DSC heating–cooling cycle test. In the vicinity of the corresponding phase transition temperature, 1 shows an obvious reversible change of dielectric plateau and small dielectric loss. The dielectric switching cycle curves show that 1 has good dielectric switching performance. All of these interesting physical properties are closely related to the reversible order–disorder states of cations and anions in the molecule. This work shows that 1 is a switchable dielectric molecular crystal material with broad application prospects, and provides a new route for design and synthesis of switchable dielectric materials with excellent properties. [ABSTRACT FROM AUTHOR]

Magnéli phase titanium oxide (TinO2n−1, 4 ≤ n ≤ 10) has wide application prospects in energy storage, catalysis and other fields. During the preparation of the TinO2n−1 phase from TiO2 by the carbothermal reduction reaction (CRR), the coexistence of multiple phases caused by the change in the reduction degree is the theoretical and practical basis for obtaining TiO2/TinO2n−1 composite materials. In this work, the H2Ti3O7 nanofiber has been employed as a precursor for the following CRR process. The X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric (TG) and Differential Scanning Calorimetry (DSC) analysis results confirmed the phase transformation process of H2Ti3O7 → TiO2(B) → anatase → rutile → TinO2n−1. Comprehensive transmission electron microscopy (TEM) characterization was carried out to investigate the phase composition and interface structures of the products calcinated at different temperatures. TiO2/Ti5O9 and λ-Ti3O5/γ-Ti3O5 interfaces with specific orientation relationships have been observed. In addition, the phase transition mechanism has also been revealed based on the structural analysis results. By carefully considering the crystal structure and symmetry of the parent and new phase, the initial lattice strain matrix based on the two observed interfaces has been established accordingly. The crystallographic features of the two types of interfaces have been calculated based on modified invariant line theory, which has confirmed the consistency of the experimental observation and calculated results. The research in this paper can further expand the applicability of the three-dimensional invariant line theory in low symmetry crystal materials. [ABSTRACT FROM AUTHOR]

An acetonitrile solvate of a Schiff base molecule (HL) with acetonitrile (HL·2CH3CN) and its Cd(II) complex (Cd(HL)2Cl2, 1) was designed and synthesized. The different conformation of HL in HL·2CH3CN is adjusted by the hydrogen bonding O–H⋯O between HL molecules, together with N–H⋯N between HL molecules and acetonitrile molecules. Meanwhile, the conformation of HL in complex 1 is adjusted by coordination interactions between Zn ions and atoms O and N, together with hydrogen bonding N–H⋯Cl. The presence of the triphenylamine group makes HL·2CH3CN and complex 1 loosely packed. Upon grinding, HL·2CH3CN and complex 1 both showed high-contrast mechanochromic luminescence (MCL) change from blue to green and cyan to yellow, respectively. These changes can be eliminated by fumigation with organic vapor. The results of powder X-ray diffraction (PXRD) show that their MCL is due to the phase transformation from a crystalline state to an amorphous state. In addition, HL·2CH3CN and complex 1 also exhibited high-contrast acidochromism upon exposure to HCl and NH3 vapor. X-ray photoelectron spectroscopy (XPS) and PXRD studies show that the protonation of the –NH– group together with phase transformation from a crystalline state to an amorphous state is attributed to the fluorescence switching. For HL·2CH3CN, the protonation process was accompanied by the departure of acetonitrile molecules. The emission of HL was restored to the amorphous state rather than the original crystalline state emission after further exposure to NH3 vapor, while 1-HCl could revert to the original crystalline state emission. In addition, HL·2CH3CN and complex 1 have been successfully used to produce writable and acid-responsive test papers. [ABSTRACT FROM AUTHOR]

[2]Pseudorotaxane, [(FcCH2NH2CH2C6H4-4-Me)(DB24C8)][PF6] ([1][PF6]; Fc = ferrocenyl and DB24C8 = dibenzo[24]crown-8-ether), undergoes crystalline phase transition at 128 °C upon heating and at 106 °C upon cooling (α-phase at low temperature; β-phase at high temperature), as shown in our previous reports. This paper presents new results from the detailed studies on the crystal phase transition of pseudorotaxane, the dielectric constant of the crystal, and the formation of a gel from a PhCl solution. The crystalline phase transition has been revealed to accompany the partial rotation of the DB24C8 molecule while maintaining the hydrogen bonds between the axle and macrocyclic component molecules. The ultrasonication of a PhCl suspension of a mixture of the axle and cyclic molecules forms a gel, which is composed of microcrystalline [1][PF6] with a new crystal form (α′-phase). The pseudorotaxane crystals with mixed counter anions, [1][PF6]1−x[Y]x (Y = AsF6 and SbF6), exist in the α- or β-phase, depending on the anion composition. Further, [1][PF6]0.28[AsF6]0.72 and [1][PF6]0.76[SbF6]0.24 are obtained in the α-phase, while [1][PF6]0.65[SbF6]0.35 crystallises in the β-phase. The phase transition temperature of the pseudorotaxane with PF6− and SbF6− counter anions is investigated using differential scanning calorimetry (DSC). [ABSTRACT FROM AUTHOR]

In this paper, a novel metal-free compound, [H2(bpyp)][ClO4]2 (1) (bpyp = 1,3-bis(4-pyridyl)propane), has been successfully synthesized. It undergoes a reversible phase transition at around Tc = 256.19 K (Tc is the Curie temperature). Compound 1 shows a moderate ferroelectric polarization (Ps) of about 0.13 μC cm−2 and a coercive field (Ec) as small as 0.65 kV cm−1. The phase transition behavior of compound 1 is well characterized by differential scanning calorimetry (DSC) and variable temperature single crystal diffraction measurements. The displacement and rotational reorientation motion of H2(bpyp)2+ cations and ClO4− anions induce the phase transition of compound 1 from the non-polar space group P21212 (No. 18) to the polar space group P21 (No. 4). The significant second harmonic generation (SHG) switching response further demonstrates the symmetry breaking from P21212 to P21. In particular, a dielectric study exhibits that the dielectric anomaly of compound 1 increases by 3–6 times at the phase transition temperature, which indicates its potential applications in switchable dielectric elements. Meanwhile, compound 1 shows semiconducting properties with a wide optical bandgap of ∼4.47 eV. This finding suggests that metal-free compounds can be used in environmentally-friendly phase transition materials, contributing to the exploration of ferroelectric–dielectric and nonlinear optical (NLO) switching materials. [ABSTRACT FROM AUTHOR]

Indications of desirable polar order in ethylammonium C2H5NH3(EtA) metal formate [EtA][Na0.5Cr0.5(HCOO)3] and the lack of it in [EtA][K0.5Cr0.5(HCOO)3] raised important questions on the origin of structural phase transition and dipolar dynamics in these kinds of compounds. In this paper we provide results of experimental studies performed on the mixed frameworks, which may give more insight into understanding these phenomena. We report the synthesis of four heterometallic metal–organic frameworks [CH3CH2NH3][KxNa0.5−xCr0.5(HCOO)3] with various compositions (x = 0, 0.04, 0.22, and 0.5). Broadband dielectric spectroscopy assisted by vibrational spectroscopy allows us to determine the role of EtA+ motions in the structural phase transition in the investigated compounds. We clearly demonstrate that the increase of the K/Na ratio results in freer translational movements of the EtA+ cations. [ABSTRACT FROM AUTHOR]

Amorphous calcium carbonate (ACC) and calcium phosphate (ACP) increasingly attract attention as initial solid phases in vertebrate and invertebrate hard tissue formation, as well as in materials science as a possible new synthetic route for advanced materials preparation. Although much is known about these two amorphous phases and similarities in the mechanisms of their formation are recognized, no attempt has been made to investigate their formation under defined and comparable initial experimental conditions, viz. supersaturation, the ratio of constituent ions, ionic strength and the presence of relevant inorganic additives. In this paper, the formation of ACC and ACP in three model precipitation systems of increased chemical complexity was investigated: (a) systems containing constituent ions, (b) systems containing additional co-ions, and (c) systems with higher ionic strength and addition of Mg2+. The results have shown that ACP is more stable and was formed at lower relative supersaturations in comparison to ACC. The precipitation domain of both phases expanded with increasing complexity of precipitation systems, with the ACP precipitation domains always being larger than those of ACC. In addition to stability, the presence of inorganic ions, especially Mg2+, influences the composition of both amorphous phases. The obtained results indicate that general similarity between ACC and ACP exists, but it could also be concluded that the similar chemical environment in which they form not necessarily leads to similar structural properties. [ABSTRACT FROM AUTHOR]

This Letter is in response to a paper by Han et al. (CrystEngComm, 2016, 18, 1563–1569) on the structures and isostructural phase transitions in (dabcoH2)(BF4)2·H2O and (dabcoH2)(ClO4)2·H2O. It is shown that the phase transitions in these compounds have a second-order character and their low-temperature phases exhibit ferroelastic properties. Thus, the transitions cannot be isostructural. The redeterminations of both crystal structures as a function of temperature evidence that at the transition points the symmetry is reduced from orthorhombic to triclinic. [ABSTRACT FROM AUTHOR]

Crystals of 4-methoxyazobenzene move on water surface and the motion is triggered by irradiation with ultraviolet light. The propulsion is produced by dissolution of the photo-generated cis isomer, which is produced by the photoinduced crystal–liquid phase transition. A photoresponsive boat was also prepared by a filter paper adsorbed with azobenzene. [ABSTRACT FROM AUTHOR]

Lead oxide is an important glass modifier not only for affecting the chemical and mechanical stabilities of glasses, but also for improving their thermal and optical properties. Since specific properties are associated with the presence of PbO, its crystallization is important to enhance the material performance. Although considerable advances have been achieved regarding the fabrication of glass-ceramic from lead-based glasses, the spatial confinement of the crystallization remains challenging. Direct laser writing (DLW) has been considered an essential technique to overcome this issue, since material properties can be changed in localized and pre-determined regions. Although DLW with femtosecond laser pulses has been widely used for glass processing, its usage for phase transformations and control of the architecture of crystals has not been much exploited. This paper reports the design and control of β-PbO and 3PbO·H2O crystalline phases in a lead borate glass using fs-DLW followed by chemical etching at room temperature. We demonstrated that the etching in aqueous KOH solution is responsible for the glass crystallization, whereas the grooves produced by fs-laser pulses enable the selective crystallization in a pre-determined 2D pattern. The method described herein is important as it can control phase transformation at the micrometer scale and also permits the growth of lead oxide and lead oxide hydrate phases, which are not achieved by heat treatment. The morphologies of these microcrystals correspond to the structure of the respective compounds, being an octahedral euhedral crystal for 3PbO·H2O and thin sheets for β-PbO crystalline phases. [ABSTRACT FROM AUTHOR]

Understanding solid–solid polymorphic transitions within molecular crystals on the molecular scale is a challenging task. It is, however, crucial for the understanding of transitions that are thought to occur through cooperative motion, which offer an interesting perspective for future applications. In this paper, we study the energy barriers and mechanisms involved in the β→αdl-norleucine transition at the molecular scale by applying different computational techniques. We conclude that the mechanism of the transition is a cooperative movement of bilayers through an intermediate state. The results indicate that local fluctuations in the conformations of the aliphatic chains play a crucial role in keeping the cooperative mechanism sustainable at large length scales. We have characterized the intermediate state. [ABSTRACT FROM AUTHOR]

Organic additives are known to help minerals grow into complex shapes, which are beneficial for achieving various functional (e.g. optical) properties. Calcite-based microlens arrays (MLAs) are good examples of functional materials produced via the self-assembly of amorphous calcium carbonate (ACC) nanoparticles followed by a heat-mediated phase transformation into calcite. The optical transparency of the MLAs is preserved due to the nanocrystalline nature of the calcite formed. In this paper, we investigate the corresponding structural changes by mapping the local lattice parameters and size of calcite crystallites within individual microlenses. We find that the driving force for producing calcite with a crystallite size of 10 nm is the minimization of residual strains and related elastic energy by plastic deformation, which includes grain boundary formation and twinning. Local strains/stresses originate from transformation-associated macroscopic volume changes, which arise because of the differences in specific volume (per CaCO3 molecule) of ACC and calcite, firstly due to water loss and then to short-order atomic rearrangements. MLAs fabricated in this way represent a striking example for a stress-engineered nanocrystalline material produced with almost no energy cost through phase transformation, as compared to grain refinement by mechanical processing. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Sb2Se on the phase change characteristics of Ge2Sb2Te5 (GST) is systemically studied for applications in phase-change random access memory (PRAM). The crystallization temperature of Sb2Se–GST increases with increasing Sb2Se content, while the archival life of the amorphous state first decreases and then increases. The phase transition from face-centered-cubic (FCC) to hexagonal (HEX) is suppressed when the Se atomic percentage is higher than 9% for Sb2Se–GST films. The wide band gap and high value of B1/2 lead to a contrast in resistance of about five orders of magnitude between the amorphous and crystalline states. Compared with GST, Ge4Sb52Te9Se35 shows a high crystallization temperature, a wider band gap and a fast switching speed, suggesting it is a potential candidate for PRAM. [ABSTRACT FROM AUTHOR]

This paper describes a study of the solvent-mediated polymorphic transformation (SMPT) of the metastable a tegafur to the thermodynamically stable ß tegafur in several solvents. Phase transformation in acetone, ethanol, i-propanol, toluene, and water at 22 °C was described using the solid-state kinetic model P2; the rate constants for this process were in the range from 0.028 min-1 to 0.0056 min-1 in all of employed solvents, an induction time was observed. Kinetic, solubility and scanning electron microscopy data indicated that nucleation kinetics corresponded to a second-order power function and according to the kinetic model, the nuclei growth rate was constant in the examined SMPT. Surface nucleation was observed, and the possible nucleation mechanism was given. The phase transition rate depended linearly on the difference between the equilibrium solubilities of a and ß tegafur in the respective solvent, i.e. supersaturation. [ABSTRACT FROM AUTHOR]

The main aim of the studies in this paper is to gain knowledge on the path of structural transformations resulting from the photocyclization in 2-tert-butylphenylphenylmethanone crystals at low and high pressures and also to carry out a comparative analysis of the results at different pressures. This work is the first example of these types of studies in scientific literature. We determined the structure of: pure reactant crystals, i.e. only containing reactant molecules, at 0.1 MPa, 0.55 GPa, 1.27 GPa and 1.50 GPa; pure product crystals, i.e. only containing product molecules, at 0.55 GPa and 1.27 GPa; and partly reacted crystals (ten structures), i.e. containing both reactant and product molecules in various proportions to each other, at 0.1 MPa (two structures), 0.55 GPa (three structures), 1.27 GPa (three structures) and 1.50 GPa (two structures). The studies have shown that (a) there is no phase transition when an increase in pressure is imposed onto the crystals, (b) the unit cell parameters change non-linearly with an increase in pressure, (c) the photochemical reaction was conducted in a homogeneous manner in the examined crystals, (d) the reaction brings about different modes of changes in the unit cell parameters at different pressures (e) the reaction proceeds faster at the end rather than at the beginning regardless of the pressure imposed onto the crystals. [ABSTRACT FROM AUTHOR]

This paper describes a methodology for the modification of phase transition temperatures using (±)-4'-methylmethcathinone solid solutions as an exemplar. This method serves to show that by varying the composition of the halide ion one can systematically alter the temperatures at which phase transitions can occur in order to evade the possibility of interconversion between polymorphs during processing or storage of materials. [ABSTRACT FROM AUTHOR]

In this paper, novel core–shell α-Fe2O3/SnO2 heterostructures (HSs) are successfully prepared by a one-step flame-assisted spray copyrolysis of iron and tin precursor. The effect of SnO2 component is investigated for the evolution of phase composition and morphology in detail. For the first time, it is noted that SnO2 as a dopant can effectively promote the phase transition of γ-Fe2O3 to α-Fe2O3 during flame synthesis. A phase-segregation induced growth mechanism is proposed to explain the formation of a unique core–shell structure. Such core–shell HSs as LIB anode materials exhibit an enhanced lithium storage capacity in comparison to pure Fe2O3 and SnO2. This enhancement could be ascribed to the synergetic effect of both single components as well as the unique core–shell HSs. [ABSTRACT FROM AUTHOR]

In this paper, a facile and economical route based on an oxidation induced phase transformation in alcoholic solution was developed to prepare mesoporous CeO2nanoflowers. The whole process could be divided into two steps: the formation of Ce(HCOO)3with flower-like structures and the oxidation induced phase transformation from Ce(HCOO)3to CeO2with unchanged morphology in the alcoholic solution. TEM results revealed that the CeO2nanoflowers consist of rods with length and diameter of 100 and 30 nm, respectively. N2adsorption/desorption experiments indicated that the CeO2nanoflowers display mesoporous structures with a mean pore size of 4 nm, and the BET surface area and pore volume of such flower-like structures are 95.7 m2g−1and 0.173 cm3g−1, respectively. Prompted by the mesoporous structure, high surface area and high pore volume, we speculate that these mesoporous CeO2flowers could be promising candidates for practical catalytic application. [ABSTRACT FROM AUTHOR]

This paper reports the transformation of rhombic dodecahedral gold nanoparticles through two different pathways depending on the water content. The gold nanoparticles were prepared by reducing HAuCl4with N,N-dimethylforamide in the presence of poly(vinyl pyrrolidone) and water. Not only the concentration of PVP but also the water content has a critical role in determining the shape transformation of the gold nanocrystals. At low water content the rhombic dodecahedron is transformed into a rhombicuboctahedron to a truncated octahedron and then to an octahedron, while at higher water content the rhombic dodecahedron is transformed into a rhombicuboctahedron and then to a cube or a truncated cube and then to a cuboctahedron and to a truncated octahedron. In addition, we demonstrated cell imaging by using the truncated octahedral, rhombic dodecahedral and octahedral gold nanoparticles as a contrast agent. [ABSTRACT FROM AUTHOR]