crystal structure

摘要： Generally,most materials expand when heated and contract when cooled,whereas negative thermal expansion(NTE)materials are very rare.As a typical NTE material,PbTiO_(3) and related compounds have drawn particular interest in recent years.The discovery of an enhanced NTE system in PbTiO_(3) is beneficial to deepen our understanding of its mechanism and regulate its properties.At present,the method of discriminating an enhanced NTE material based on PbTiO_(3) is not universal.Here,we propose a semi-empirical method through evaluating the average lattice distortion in related systems to estimate the relative coefficient of thermal expansion conveniently.The rationality of the method was verified by the analysis of the 0.6PbTiO_(3)-0.4Bi(Ga_(x)Fe_(1-x))O_(3) system.So far,all PbTiO_(3)-based compounds with enhanced NTE conform well to this method.This method provides the possibility to find more enhanced NTE PbTiO_(3)-based materials.

摘要： The oxygen fugacity(f_(O2)) may affect the ionic conductivity of olivine under upper mantle conditions because Mg vacancies can be produced in the crystal structure by the oxidization of iron from Fe^(2+) to Fe3+. Here we investigated olivine ionic conductivity at 4 GPa, as a function of temperature, crystallographic orientation, and oxygen fugacity, corresponding to the topmost asthenospheric conditions. The results demonstrate that the ionic conductivity is insensitive to f_(O2) under relatively reduced conditions(f_(O2) below Re-ReO_(2) buffer), whereas it has a clear f_(O2)-dependence under relatively oxidized conditions(f_(O2) around the magnetite-hematite buffer). The ionic conduction in olivine may contribute significantly to the conductivity anomaly in the topmost asthenosphere especially at relatively oxidized conditions.

摘要： The work addresses to the study of the molecular and crystal structure and properties of a new energyintensive compound 3,6-bis(2,2,2-trinitroethylnitramino)-1,2,4,5-tetrazine(NBTAT),first obtained by the authors in 2020.NBTAT compound crystallizes in the monoclinic system,space group P2(1)/n,density at room temperature 1.939 g/cm^(3).The energies of crystal packing and pairwise intermolecular interactions in NBTAT and its unnitrated analogue BTAT were calculated,and their comparative analysis was carried out.The enthalpy of formation of NBTAT molecules was calculated by quantum-chemical methods using Gaussian 09,and the enthalpy of formation of NBTAT in the solid phase(618 kJ/mol)was estimated.The energy capabilities of NBTAT as an oxidizer of solid composite propellants are estimated.It is shown that in metal-free compositions NBTAT is significantly superior to ammonium perchlorate(AP),dinitramide ammonium salt(ADN),HMX,BTAT at all stages of rocket systems,and is comparable to the superdense CL-20 yielding to the latter at the lower stages and slightly winning at the upper stages.

摘要： Optical computing and optical neural network have gained increasing attention in recent years because of their potential advantages of parallel processing at the speed of light and low power consumption by comparison with electronic computing.The optical implementation of the fundamental building blocks of a digital computer,i.e.logic gates,has been investigated extensively in the past few decades.Optical logic gate computing is an alternative approach to various analogue optical computing architectures.In this paper,the latest development of optical logic gate computing with different kinds of implementations is reviewed.Firstly,the basic concepts of analogue and digital computing with logic gates in the electronic and optical domains are introduced.And then a comprehensive summary of various optical logic gate schemes including spatial encoding of light field,semiconductor optical amplifiers(SOA),highly nonlinear fiber(HNLF),microscale and nanoscale waveguides,and photonic crystal structures is presented.To conclude,the formidable challenges in developing practical all-optical logic gates are analyzed and the prospects of the future are discussed.

摘要： The quasicrystal phase is beneficial to increasing the strength of magnesium alloys.However,its complicated structure and unclear phase relations impede the design of alloys with good mechanical properties.In this paper,the Mg_(40)Zn_(55)Nd_(5) icosahedral quasicrystal(I-phase)structure is discovered in an as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).A cloud-like morphology is observed with Mg_(41.6)Zn_(55.0)Nd_(3.4) composition.The selected area electronic diffrac-tion(SAED)analysis shows that the icosahedral quasicrystal structure has 5-fold,4-fold,3-fold,and 2-fold symmetry zone axes.The thermo-dynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry(DSC)in the annealed alloys.When an-nealed above 300°C,the Mg_(40)Zn_(55)Nd_(5) quasicrystal is found to decompose into a stable ternary phase Mg_(35)Zn_(60)Nd_(5),a binary phase MgZn,andα-Mg,suggesting that the quasicrystal is a metastable phase in the Mg-Zn-Nd system.

摘要： The title compound, FeCl4(C5N2H6)(C5N2H5) consists of two [(C5N2H6) (C5N2H5)]+ organic cations and [FeCl4]- anion. The geometry of the iron ion is tetrahedral, formed by four chlorine atoms. The complex was characterized by single crystal X-ray diffraction, Fourier Transform Infrared spectroscopy, thermal analysis and UV-Visible spectroscopy. Hirshfeld surface analysis was also used for understanding the intermolecular interactions in the crystal packing. Single-crystal X-ray diffraction analysis indicates that this complex crystallizes in the monoclinic system, P21/c space group with a = 7.598 (3) Å, b = 13.694 (4) Å, c = 17.105 (5) Å, β = 97.203 (6)° V = 1765.7 (10) Å3 and Z = 4. The [FeCl4]- anion and [(C5N2H6)(C5N2H5)]+ cations are linked through three-dimensional hydrogen-bonding network consisting of N-H...Cl and π-π interactions. Hirshfeld surface analysis and the related 2D fingerprint plots reveal that the complex is dominated by N-H...Cl contacts.

摘要： Two-dimensional(2D)black arsenic phosphorus(b-AsP),as an alloy of black phosphorus(bP)with arsenic,has attracted great attention because of its outstanding electronic and optical properties,including high carrier mobility,tunable bandgap and in-plane anisotropy.B-AsP has a smaller bandgap(0.15–0.3 eV)than the b-P bandgap(0.3–2.0 eV),and thus can be used for mid-infrared photodetectors.In addition,both of them can form various van der Waals(vdW)heterojunctions with other 2D materials to realize novel functional optoelectronic devices.Here,we compare the basic characteristics of b-AsP and b-P,including crystal structure,optical properties,band structure,electrical properties and stability,and we summarize the update progress of b-AsP in photo detection,including representatives of phototransistor and photodiode devices.In the last part,the future research directions are discussed.

摘要： This study was designed to solve the problem of large waste volume from bamboo processing residues in recent years.Using magnesium oxychloride(MO)cementitious material as the main material and bamboo residue(BR)as the reinforcing material,a BR/MO composite material was prepared.The effects of BR amount on the molding properties,mechanical strength,and water resistance of BR/MO composites were examined and discussed.Scanning electron microscopy(SEM),X-ray diffractometry(XRD),and thermogravimetric analysis were used to characterize composite microscopic morphology,crystalline structure,and heat resistance.The results showed that,when the BR content was 1.00%(by wt),the flowability of MO paste was beneficial to composite molding.Composite mechanical properties and water resistance were greatly affected by BR addition.When the BR content was 1.00%,composite compressive and bending strengths and softening coefficient all reached maximum values.Meanwhile,increases in water absorption by 24 h and decreases of contact angle were small.These results suggested that,when the BR content was 1.00%,composite mechanical properties and water resistance were the best and the mechanical strength also improved with extended composite storage time.SEM analysis indicated that BR played the role of a reinforcing phase in MO matrices.However,when the BR content exceeded 1.00%,interfacial bonding between BR and MO became less.XRD analysis showed that,with 1.00%BR content,composites showed more 5-phase crystals with high strength.This further explained the reason why this composite’s mechanical properties were the best and the heat resistance not deteriorated due to BR,which was easily decomposed.

摘要： Rice ratooning,or the production of a second rice crop from stubble after the harvest of the main crop,is considered to be a green and resource-efficient rice production system.The present study was conducted to examine variance in amylose content(AC),grain morphology,crystal structure,and thermal properties of starch between main-and ratoon-season rice of seven varieties.Ratoon-season rice grains had higher ACs and significantly lower transition gelatinization temperatures(To,Tp,and Tc)than did main-season rice grains.The relative crystallinity and lamellar peak intensity of ratoon-season rice starch were 7.89%and 20.38%lower,respectively,than those of main-season rice starch.In addition,smaller granules with smoother surfaces and lower thermal parameters were observed in the starch of ratoon-season rice.The relative crystallinity and lamellar peak intensity of starch correlated negatively with the AC and positively with transition gelatinization temperatures.These results suggest that the superior cooking quality of ratoon-season rice is attributable to the moderate increase of grain AC,which reduces the relative crystallinity,weakens the crystal structure,and lead to a decrease in the gelatinization temperature.

摘要： Layered metal-organic polymer [Co(L)6](NO3)2 was obtained (where, L = C3H4N2) and structurally characterized by X-Ray diffraction (XRD) analysis. Crystals have trigonal structure: a = b = 12.3555(10) Ǻ, c = 14.4833(3) Ǻ;α = β = 90˚;γ = 120˚;V = 1914.78(5) Ǻ;R3, Z = 3. The structure of the complex consists of discrete [Co(L)6]2+ cations and anions. The Co2+ ion has a centrosymmetric octahedron configuration with a coordination site—CoN6. The ligand is coordinated monodentate through the pyridine nitrogen atom (N3) to the Co2+ ion with an average Co-N bond distance of 2.1590 Ǻ. Molecules in the coordination polymer are additionally linked by intermolecular hydrogen bonds through the pyrrole nitrogen atom (-N-H) and oxygen of the nitrate group with the formation of a polymer chain of the type: N-H…O. The chains are linked in layers along the (001) plane.

摘要： The crystal structure of [Cu2(NO3)2(IM-1'-MeBzIm)2(dca)2](IM-1'-MeBzIm=2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl, dca=dicyanamide anion) triclinic, space group P-1, Z=1. Crystal data: C34H40Cu2N16O8, Mr=927.90, a=9.440(5), b=10.124(6)), c=11.603(7) (A), β=94.033(6)° V=1038.2(10) (A)3, Dc=1.484 g/cm3, μ(MoKα)=1.093 mm-1, F(000)=478, R=0.0609 and wR=0.1512 for 2456 observed reflections with Ⅰ＞2σ(Ⅰ). The magnetic properties for the title complex has been investigated in the temperature range 2 ～300 K and there are ferromagnetic interactions between the coordinated nitronyl nitroxides(J=12.46 cm-1) and intramolecular ferromagnetic interactions.

摘要： The crystal structure of [Cu2(NO3)2(IM-1'-MeBzIm)2(dca)2](IM-1'-MeBzIm=2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl, dca=dicyanamide anion) triclinic, space group P-1, Z=1. Crystal data: C34H40Cu2N16O8, Mr=927.90, a=9.440(5), b=10.124(6)), c=11.603(7) (A), β=94.033(6)° V=1038.2(10) (A)3, Dc=1.484 g/cm3, μ(MoKα)=1.093 mm-1, F(000)=478, R=0.0609 and wR=0.1512 for 2456 observed reflections with Ⅰ＞2σ(Ⅰ). The magnetic properties for the title complex has been investigated in the temperature range 2 ～300 K and there are ferromagnetic interactions between the coordinated nitronyl nitroxides(J=12.46 cm-1) and intramolecular ferromagnetic interactions.

摘要： The crystal structure of [Cu2(NO3)2(IM-1'-MeBzIm)2(dca)2](IM-1'-MeBzIm=2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl, dca=dicyanamide anion) triclinic, space group P-1, Z=1. Crystal data: C34H40Cu2N16O8, Mr=927.90, a=9.440(5), b=10.124(6)), c=11.603(7) (A), β=94.033(6)° V=1038.2(10) (A)3, Dc=1.484 g/cm3, μ(MoKα)=1.093 mm-1, F(000)=478, R=0.0609 and wR=0.1512 for 2456 observed reflections with Ⅰ＞2σ(Ⅰ). The magnetic properties for the title complex has been investigated in the temperature range 2 ～300 K and there are ferromagnetic interactions between the coordinated nitronyl nitroxides(J=12.46 cm-1) and intramolecular ferromagnetic interactions.

摘要： The crystal structure of [Cu2(NO3)2(IM-1'-MeBzIm)2(dca)2](IM-1'-MeBzIm=2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl, dca=dicyanamide anion) triclinic, space group P-1, Z=1. Crystal data: C34H40Cu2N16O8, Mr=927.90, a=9.440(5), b=10.124(6)), c=11.603(7) (A), β=94.033(6)° V=1038.2(10) (A)3, Dc=1.484 g/cm3, μ(MoKα)=1.093 mm-1, F(000)=478, R=0.0609 and wR=0.1512 for 2456 observed reflections with Ⅰ＞2σ(Ⅰ). The magnetic properties for the title complex has been investigated in the temperature range 2 ～300 K and there are ferromagnetic interactions between the coordinated nitronyl nitroxides(J=12.46 cm-1) and intramolecular ferromagnetic interactions.

摘要： Recently, intense interest has been focused on studies of cubane-like poly-nuclear complexes due to their relevance to multi-electron transfer centers systems, and to their interesting properties .Tetranuclear cubane-like Ni complexes have been extensively investigated since the pioneering work of Andrew and Blake . A number of cubane-like complexes involving bridging ome, or alkoxo have beenpreviously reported. To understand the active role the transition metal ion played in the process of organicsynthesis and interestine molecular nrooerties.

摘要： Recently, intense interest has been focused on studies of cubane-like poly-nuclear complexes due to their relevance to multi-electron transfer centers systems, and to their interesting properties .Tetranuclear cubane-like Ni complexes have been extensively investigated since the pioneering work of Andrew and Blake . A number of cubane-like complexes involving bridging ome, or alkoxo have beenpreviously reported. To understand the active role the transition metal ion played in the process of organicsynthesis and interestine molecular nrooerties.

摘要： Recently, intense interest has been focused on studies of cubane-like poly-nuclear complexes due to their relevance to multi-electron transfer centers systems, and to their interesting properties .Tetranuclear cubane-like Ni complexes have been extensively investigated since the pioneering work of Andrew and Blake . A number of cubane-like complexes involving bridging ome, or alkoxo have beenpreviously reported. To understand the active role the transition metal ion played in the process of organicsynthesis and interestine molecular nrooerties.

摘要： Recently, intense interest has been focused on studies of cubane-like poly-nuclear complexes due to their relevance to multi-electron transfer centers systems, and to their interesting properties .Tetranuclear cubane-like Ni complexes have been extensively investigated since the pioneering work of Andrew and Blake . A number of cubane-like complexes involving bridging ome, or alkoxo have beenpreviously reported. To understand the active role the transition metal ion played in the process of organicsynthesis and interestine molecular nrooerties.

摘要： A novel complex [Na(NIT-1'-MeBzIm)3]ClO4 (NIT-1'-MeBzIm=2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been prepared and structurally characterized by elemental analysis, IR spectra and X-ray diffraction methods. The title complex crystallizes in Trigonal,space group P-3, Z= 2. Crystal data: C45H57ClN12NaO10, Mr=984.47, a=13.9411(8), b=13.9411(8), c=14.8622(16) (A), γ= 120°,V= 2501.5(3) (A)3, Dc =1.307g/cm3, μ(MoKα) =0.152 mm-1, F(000) =1038, R=0.0637, wR =0.1813, for 1957 observed reflections with Ⅰ＞2σ(Ⅰ). X-ray analysis reveals that Na(I) ion is six-coordinated with three NIT-1'-MeBzIm radicals. As we known, the coordinated way of three radicals coordinating to Na(I) ion by chelated way in main group is the first example.

摘要： A novel complex [Na(NIT-1'-MeBzIm)3]ClO4 (NIT-1'-MeBzIm=2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been prepared and structurally characterized by elemental analysis, IR spectra and X-ray diffraction methods. The title complex crystallizes in Trigonal,space group P-3, Z= 2. Crystal data: C45H57ClN12NaO10, Mr=984.47, a=13.9411(8), b=13.9411(8), c=14.8622(16) (A), γ= 120°,V= 2501.5(3) (A)3, Dc =1.307g/cm3, μ(MoKα) =0.152 mm-1, F(000) =1038, R=0.0637, wR =0.1813, for 1957 observed reflections with Ⅰ＞2σ(Ⅰ). X-ray analysis reveals that Na(I) ion is six-coordinated with three NIT-1'-MeBzIm radicals. As we known, the coordinated way of three radicals coordinating to Na(I) ion by chelated way in main group is the first example.