Si_2O_2 molecule:structure of ground state and the excited properties under different external electric fields

Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory （DFT） at the level of cc-pvtz and 6-311-k＋G^＊＊. It is found that the optimizing value by B31yp/cc-pvtz is closer to the experimental data. The excited properties under different external electric fields are also investigated by the time-dependent-DFT method. Transitions from the ground state of Si2O2 molecule to the first singlet state under different external electric fields can take place more easily. The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV.

Interface properties and electronic structures of aromatic molecules with anhydride and thio-functional groups on Ag(111) and Au(111) substrates

First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag(111) and Au(111)reveal that the self-assembly structures and the interface properties are mainly determined by the functional groups of aromatic molecules. Detailed investigations of the electronic structures show that the electrons in molecular backbone are redistributed and charge transfer occurs through the bond between the metal and the functional groups after these molecules have been deposited on a metal substrate. The interaction between Ag(111)(or Au(111)) and aromatic molecules with anhydride functional groups strengthens the π bonds in the molecular backbone, while that between Ag(111)(or Au(111))and aromatic molecules with sulfur weakens the π bonds. However, the intrinsic electronic structures of the molecules are mostly conserved. The large-sized aromatic backbone has less influence on the nature of electronic structures than the small-sized one, either at the interface or at the molecules. These results are useful to build the good metal-molecule contact in molecule-based devices.

Preparation and Fluorescence Properties of Co-doped Nanocomposite Film Based on Supra Molecular Structure

A novel materials design procedure based on the co-doping of metal nanoparticle and azo dye compound （MNPADC） is developed to improve the properties of functional molecules. The synthesized materials were characterized by transmission electron micrograph （TEM）, ultraviolet-visible absorption spectra （UV-Vis） and fluorescence spectra （FS）. It was found that the fluorescence intensity of methyl orange （MO） was enhanced by 5 times in the aqueous composite system doped with silver nanoparticles whereas it was reduced by 15% and 20% in composite films with co-mixing and coating structures, respectively. The results indicate that the properties of functional molecules can be greatly improved in composite film with supra molecular structure and that the procedure presented here is effective.

A review on the multi-scaled structures and mechanical/thermal properties of tool steels fabricated by laser powder bed fusion additive manufacturing

The laser powder bed fusion(LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest,especially in the molds industry.The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds.Thus,LPBF-processed tool steels have attracted more and more attention.The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels.This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena,the microstructural characteristics,and the mechanical/thermal properties,including tensile properties,wear resistance,and thermal properties.The microstructural characteristics are presented through a multiscale perspective,ranging from densification,meso-structure,microstructure,substructure in grains,to nanoprecipitates.Finally,a summary of tool steels and their challenges and outlooks are introduced.

First‑principles study on electronic structure,optical and magnetic properties of rare earth elements X(X=Sc,Y,La,Ce,Eu)doped with two‑dimensional GaSe

The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.

Theoretical insights into the structures and fundamental properties of pnictogen nitrides

Recent experimental advancements reported a chemical reaction between antimony and nitrogen under high temperature and high pressure,yielding crystalline antimony nitride(Sb_(3)N_(5))with an orthorhombic structure.Motivated by this statement,we calculate the stability,elastic properties,electronic properties and energy density of the Cmc2_(1) structure for pnictogen nitrides X_(3)N_(5)(X=P,As,Sb,and Bi)using first-principles calculations combined with particle swarm optimization algorithms.Calculations of formation enthalpies,elastic constants and phonon spectra show that P_(3)N_(5),As_(3)N_(5) and Sb_(3)N_(5) are thermodynamically,mechanically and kinetically stable at 35 GPa,whereas Bi_(3)N_(5) is mechanically and kinetically stable but thermodynamically unstable.The computed electronic density of states shows strong covalent bonding between the N atoms and the phosphorus group atoms in the four compounds,confirmed by the calculated electronic localization function.We also calculate the energy densities for Sb_(3)N_(5) and find it to be a potentially high-energy-density material.

Effect of strain on structure and electronic properties of monolayer C_(4)N_(4)

The first-principles calculations are performed to examine structural,mechanical,and electronic properties at large strain for a monolayer C_(4)N_(4),which has been predicted as an anchoring promising material to attenuate shuttle effect in Li–S batteries stemming from its large absorption energy and low diffusion energy barrier.Our results show that the ideal strengths of C_(4)N_(4)under tension and pure shear deformation conditions reach 13.9 GPa and 12.5 GPa when the strains are 0.07 and 0.28,respectively.The folded five-membered rings and diverse bonding modes between carbon and nitrogen atoms enhance the ability to resist plastic deformation of C_(4)N_(4).The orderly bond-rearranging behaviors under the weak tensile loading path along the[100]direction cause the impressive semiconductor–metal transition and inverse semiconductor–metal transition.The present results enrich the knowledge of the structure and electronic properties of C_(4)N_(4)under deformations and shed light on exploring other two-dimensional materials under diverse loading conditions.

Effect of Fe_(2)O_(3)on the Structure,Physical Properties and Crystallization of CaO-Al_(2)O_(3)-SiO_(2)Glass

The calcium aluminosilicate-based glasses(CaO-Al_(2)O_(3)-SiO_(2),CAS)with different Fe_(2)O_(3)content(0.10wt%,0.50wt%,0.90wt%,and 1.30wt%)were prepared by traditional melt-quenching method.The glass network structure,thermal and mechanical properties,and crystallization behavior changes were investigated by nuclear magnetic resonance spectrometer,Fourier-transform infrared spectro-photometer,X-ray diffractometer,differential scanning calorimetry and field emission scanning electron microscope measurements.The change of Q^(n)in glass structures reveals the glass network connectivity decreases due to the increasing content of Fe_(2)O_(3)addition,resulting in the increasing of non-bridging number in glass structure.The glass densities slightly rise from 2.644 to 2.681 g/cm^(3),while Vickers’s hardness increases at first,from 6.469 to 6.901 GPa,then slightly drops to 6.745 GPa,with Fe_(2)O_(3)content increase.There is almost no thermal expansion coefficient change from different Fe_(2)O_(3)content.The glass transmittance in visible range gradually decreases with higher Fe_(2)O_(3)content,resulting from the strong absorption of Fe^(2+)and Fe^(3+)ions.The calculated activation energy from thermal analysis results first decreases from 282.70 to 231.18 kJ/mol,and then increases to 244.02 kJ/mol,with the Fe_(2)O_(3)content increasing from 0.10wt%to 1.30wt%.Meanwhile,the maximum Avrami constant of 2.33 means the CAS glasses exhibit two-dimensional crystallization.All of the CAS glass-ceramics samples contain main crystal phase of anorthite,the microstructure appears lamellar and columnar crystals.

Design and additive manufacturing of bionic hybrid structure inspired by cuttlebone to achieve superior mechanical properties and shape memory function

Lightweight porous materials with high load-bearing,damage tolerance and energy absorption(EA)as well as intelligence of shape recovery after material deformation are beneficial and critical for many applications,e.g.aerospace,automobiles,electronics,etc.Cuttlebone produced in the cuttlefish has evolved vertical walls with the optimal corrugation gradient,enabling stress homogenization,significant load bearing,and damage tolerance to protect the organism from high external pressures in the deep sea.This work illustrated that the complex hybrid wave shape in cuttlebone walls,becoming more tortuous from bottom to top,creates a lightweight,load-bearing structure with progressive failure.By mimicking the cuttlebone,a novel bionic hybrid structure(BHS)was proposed,and as a comparison,a regular corrugated structure and a straight wall structure were designed.Three types of designed structures have been successfully manufactured by laser powder bed fusion(LPBF)with NiTi powder.The LPBF-processed BHS exhibited a total porosity of 0.042% and a good dimensional accuracy with a peak deviation of 17.4μm.Microstructural analysis indicated that the LPBF-processed BHS had a strong(001)crystallographic orientation and an average size of 9.85μm.Mechanical analysis revealed the LPBF-processed BHS could withstand over 25000 times its weight without significant deformation and had the highest specific EA value(5.32 J·g^(−1))due to the absence of stress concentration and progressive wall failure during compression.Cyclic compression testing showed that LPBF-processed BHS possessed superior viscoelastic and elasticity energy dissipation capacity.Importantly,the uniform reversible phase transition from martensite to austenite in the walls enables the structure to largely recover its pre-deformation shape when heated(over 99% recovery rate).These design strategies can serve as valuable references for the development of intelligent components that possess high mechanical efficiency and shape memory capabilities.

Structure,electronic,and nonlinear optical properties of superalkaline M_(3)O(M=Li,Na)doped cyclo[18]carbon

Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs.In this paper,the geometry,bonding properties,electronic structure,absorption spectrum,and nonlinear optical(NLO)properties of superalkaline M_(3)O(M=Li,Na)-doped cyclo[18]carbon were studied by using density functional theory.M_(3)O and the C_(18) rings are not coplanar.The C_(18) ring still exhibits alternating long and short bonds.The charge transfer between M_(3)O and C_(18) forms stable[M_(3)O]+[C_(18)]-ionic complexes.C_(18)M_(3)O(M=Li,Na)shows striking optical nonlinearity,i.e.,their first-and second-order hyperpolarizability(βvec andγ||)increase considerably atλ=1907 nm and 1460 nm.

Mechanical Properties and Electronic Structures of M(M=Ti,V,Cr,Mn and Fe)Dopedβ-Si_(3)N_(4) from First-Principle

The structures,mechanical properties and electronic structures of M metals(M=Ti,V,Cr,Mn and Fe)dopedβ-Si_(3)N_(4) were investigated by First-principles calculations within CASTEP.The calculated lattice parameters ofβ-Si_(3)N_(4) were consistent with previous date.The cohesive energy and formation enthalpy show that initialβ-Si_(3)N_(4) has the highest structural stability.The calculated elastic constant and the Voigt-Reuss-Hill approximation indicate that elastic moduli ofβ-Si_(3)N_(4) are slightly reduced by M doping.Based on Poisson’s and Pugh’s ratio,β-Si_(3)N_(4) is a ductile material and the toughness ofβ-Si_(3)N_(4) increases with M doping,and Fe doping exhibited the best toughness.The results of density of states,charge distributions and overlapping populations indicate thatβ-Si_(3)N_(4) has the strong covalent and ionic bond strength between N and Si.

Synthesis,crystal structure and photo-physical properties of tris(4-methyl-2,5-diphenylpyridine)iridium for OLED

Organic light-emitting diodes(OLEDs)have important applications in the field of next-generation displays and lighting,and phosphorescent iridium complexes are an important class of electroluminescent phosphorescent materials.In this paper,Ir(bmppy)_(3),tris(4-methyl-2,5-diphenylpyridine)iridium,was synthesized and elvaluted for photo-physical characteristics.Single crystals suitale for X-ray diffraction(XRD)were grown from a mixture solvent of dichloromethane and absolute ethanol.The composition and structur of Ir(bmppy)_(3)were determined by element analysis,NMR spectra and XRD.The complex crystallizes in the monoclinic symmetry with the space group P21/c with a slightly distorted octahedral configuration.As measured by UV-Visible and photoluminescence spectra,Ir(bmppy)_(3) displays a maximum emission at at 527 nm at ambient temperature,a typical green-emitting profile.The complex has potential for application in the OLED industry.

Syntheses,structures,and properties of three coordination polymers based on 5⁃ethylpyridine⁃2,3⁃dicarboxylic acid and N⁃containing ligands

Three coordination polymers[Mn(epda)(2,2'⁃bipy)(H_(2)O)](1),[Mn(epda)(phen)](2),and[Co_(2)(epda)2(bpe)2(H_(2)O)_(4)]·5H_(2)O(3)(H2epda=5⁃ethyl⁃pyridine⁃2,3⁃dicarboxylic acid,2,2'⁃bipy=2,2'⁃bipyridine,phen=phenanthroline,bpe=1,2⁃bis(4⁃pyridyl)ethylene)were synthesized by solvothermal reactions and characterized by single⁃crystal X⁃ray diffraction,thermogravimetric analyses,IR spectroscopy and elemental analysis.1 displays a 1D chain struc⁃ture,and these chains are joined by O-H…O hydrogen bonding andπ⁃πstacking interactions to generate a 2D layer structure.2 displays a 2D layer structure,and adjacent layers are generated 3D architecture throughπ⁃πstacking interactions.3 displays a 1D chain structure,and adjacent chains are generated double layer structure through O-H…O hydrogen bonding.The fluorescent properties of 1 and 3 indicate that they can potentially be used as a luminescent sensor.1 was highly selective and sensitive towards o⁃nitrophenol through different detection mechanisms,however,3 was highly selective and sensitive towards 2,4,6⁃trinitrophenol.In addition,the magnetic behavior of 2 has also been investigated.CCDC:2172533,1,2355773,2,2355774,3.

Effect of Property Tax on Optimization and Upgrading of Industrial Structure

China's economic growth and economic development has entered a new stage,and the optimization and upgrading of industrial structure is the core driving force for China to achieve high-quality economic development during the"14 th Five-Year Plan"period.Property tax has a conductive effect on the upgrading of industrial structure.Therefore,from the perspective of property tax and industrial structure adjustment and the relationship between them,this study summarizes the relevant research of domestic and foreign scholars.On the basis of the research,the paper puts forward some relevant policy suggestions on improving China's property tax and promoting the optimization and upgrading of China's industrial structure.

Analysis of the Molecules Structure and Vertical Electron Affinity of Organic Gas Impact on Electric Strength

It is necessary to find an efficient selection method to pre-analyze the gas electric strength from the perspective of molecule structure and the properties for finding the alternative gases to sulphur hexafluoride （SF6）. As the properties of gas are determined by the gas molecule structure, the research on the relationship between the gas molecule structure and the electric strength can contribute to the gas pre-screening and new gas development. In this paper, we calculated the vertical electron affinity, molecule orbits distribution and orbits energy of gas molecules by the means of density functional theory （DFT） for the typical structures of organic gases and compared their electric strengths. By this method, we find part of the key properties of the molecule which are related to the electric strength, including the vertical electron affinity, the lowest unoccupied molecule orbit （LUMO） energy, molecule orbits distribution and negativeion system energy. We also listed some molecule groups such as unsaturated carbons double bonds （C=C） and carbonitrile bonds （C=N） which have high electric strength theoretically by this method.

First-Principle Study on the Electronic Structure and Optical Property of New Diluted Magnetic Semiconductor(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO

The band structure,DOSs,and optical properties of(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO,including dielectric function,absorption function,reflection function,and energy loss spectrum were studied by using the first-principles calculation.The calculation results indicate that(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO is a direct bandgap semiconductor with a bandgap of 1.1 eV.The Fermi surface is asymmetric and exhibits spin splitting phenomenon.The new type of dilute magnetic semiconductor(Y_(0.75)Ca_(0.25))(Cu_(0.75)Mn_(0.25))SO exhibits significant light loss around 70 eV,with light reflection gradually increasing after 30 eV,and light absorption mainly occurring around 8-30 eV.These results also provide a basis for the discovery of more types of 1111 phase new dilute magnetic semiconductors in the future.

Structure and Properties of Self-reinforced Material Made from Ultra-high Molecular Weight Polyethylene-montmorillonite Nanocomposite

High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.

Molecular Structures and Mechanical Properties of Microbe Rapid Coagulation Natural Rubber

In this work,molecular structures,dynamic mechanical properties and glass transition temperatures of microbe coagulated natural rubber（NR） samples were analyzed by using pyrolysis gas chromatography-mass spectrometry（py-GC/MS）,rubber process analyzer（RPA） and dynamic mechanical thermal analysis（DMA）.And the cross-linked network structures and mechanical properties of the corresponding NR vulcanizates were further determined by using nuclear magnetic resonance（NMR） crosslink density spectrometer（XLDS-15） and universal testing machines.The results show that NR raw rubber produced by rapidly coagulated with microorganism exhibits a simple molecular structure composition and good dynamic mechanical properties,and the corresponding NR vulcanizates possess the aggregation structure of high cross-linked density,a high glass transition temperature of-61.5 ℃ and high mechanical properties（tensile strength reaches 25.2 MPa）,as compared with that coagulated with acetic acid.

Probing the structure of multi-center molecules with odd–even high harmonics

We study high-order harmonic generation(HHG)from multi-center asymmetric linear molecules numerically and analytically.Our simulations show that odd and even HHG spectra of the asymmetric multi-center system respond differently to the change of the molecular structure.Specifically,when the internuclear distances between these nuclei of the molecule have a small change,the odd spectra usually do not change basically,but the even spectra differ remarkably.Based on this phenomenon,a simple procedure is proposed to probe the positions of these nuclei with odd–even HHG.Our results shed light on attosecond probing of the structure of multi-center molecules using HHG.

Crystal Structure and Binding Properties of a New Molecular Clip Based on Diethoxycarbonyl Glycoluril: C_(42)H_(36)N_6O_6

A new molecular clip based on diethoxycarbonyl glycoluril 5： C42H36N6O6, has been synthesized and characterized by single-crystal X-ray diffraction. The crystal belongs to orthorhombic, space group Pbca with a = 12.7639（5）, b = 16.9727（7）, c = 34.2069（14） A, V = 7410.5（5） A3, Z = 8, Dc= 1.292 g/cm3, p（MoKa） = 0.088 mm-1, F（000） = 3024, the final R = 0.0655 and wR = 0.1566 for 5123 observed reflections with I 〉 2tr（/）. The crystal structural analysis shows that intermolecular C-H...O and C-H...N hydrogen bonds stabilized the whole crystal structure. The binding study by fluorescence spectroscope titration showed that the title molecule can selectively recognize Fe3~ with fluorescence quenching.