Infrared(IR)nonlinear optical(NLO)materials have attracted tremendous interest for civil and military applications,but it remains a great contemporary challenge to develop high-effciency NLO crystals that possess suff...Infrared(IR)nonlinear optical(NLO)materials have attracted tremendous interest for civil and military applications,but it remains a great contemporary challenge to develop high-effciency NLO crystals that possess suffciently high second-harmonic generation(SHG)effciencies coupled to wide transparency ranges and high laser damage thresholds.A series of new hydrous rare-earth iodates RE(IO_(3))_(3)·(H_(2)O)(RE=Y 1,Eu 2)and La_(2)(IO_(3))_(6)(H_(2)O)(3)have been synthesized through facile hydrothermal methods.1 and 2 are isostructural,crystallizing in the polar space group P21,while 3 crystallizes in the polar space group Pc.1-3 feature three-dimensional(3D)frameworks composed of alternately connected corner-shared dis torted[REO_(x)]polyhedra(RE=Y,Eu,and La;x=8,9)and[IO_(3)]^(−)groups.Optical studies showed that 1–3 exhibit good NLO properties,including strong SHG intensities(3.0×(1),4.5×(2),and 1.5×KH_(2)PO_(4)(3)),large band gaps(4.12(1),4.36(2),and 4.24 eV(3),with 2 possessing the largest band gap among the known SHG-active rare-earth-based iodates,high laser damage thresholds(LDT)(53×(1),43×(2),and 44×AgGaS_(2)(3)),and wide transparency ranges(ca.3.0–11.3μm)in the mid-IR region covering two criti cal IR transparency windows;1–3 are therefore potential candidate NLO materials.Density functional theory calculations on 1–3 confirm that their strong SHG responses and large band gaps are mainly derived from the synergistic effect of[IO_(3)]^(−)groups and rare-earth oxide polyhedra[REOx]in their 3D frameworks.We conclude that the introduction of rare-earth cations with moderate electropositivity into iodates may optimize the balance between SHG effciency and optical band gaps,the key requirement for high-performance NLO materials for practical applications.展开更多
A hydrodynamic approach is used to investigate a three-component magnetized plasma sheath which consists of electrons and two species of positive ions. Assuming a phase space of one-dimensional spatial coordinate syst...A hydrodynamic approach is used to investigate a three-component magnetized plasma sheath which consists of electrons and two species of positive ions. Assuming a phase space of one-dimensional spatial coordinate system and three-dimensional velocity coordinate system, the effect of different concentrations of positive ion species on some characteristics of the plasma sheath such as the velocity and density distribution of positive ion species and the electrostatic potential of this region is investigated. The calculated results show that the increase in the density ratio of positive ion species causes a decrease in both the ion velocities and the electrostatic potential of the sheath region. Also, it is shown that in the sheath region of a magnetized plasma consisting of only one positive ion species the bumps of the net density of charged particles disappears much faster. In addition, three-dimensional velocity of each positive ion species in the sheath region is plotted for different concentrations of positive ion species.展开更多
The study of new,unusual structures and reactivity patterns is of great interest for various field of organic and organometallic chemistry.Metallacycles of electropositive transition metals represent an excellent plat...The study of new,unusual structures and reactivity patterns is of great interest for various field of organic and organometallic chemistry.Metallacycles of electropositive transition metals represent an excellent platform for this purpose.In this work,we present the synthesis,characterisation,and reactivity toward carbodiimides of a set of ring-strained group 4 ansa-metallocene-based 1-metallacyclobuta-2,3-dienes Cp’_(2)M(Me_(3)SiC_(3)SiMe_(3))(M=Ti,Zr;Cp’_(2)=indenyl or tetrahydroindenyl based ansa-Cp ligand).In line with experimental studies,computational analysis of the electronic structure of new and previously reported 1-metallacyclobuta-2,3-dienes for the first time shows that the biradical character of these species not only depends on the metal,but also strongly on the nature of the cyclopentadienyl ligands.In reactions with carbodiimides RNvCvNR,depending on the substituents of the carbodiimide,either 2-aza-1-metallacyclobut-3-ene(R=iPr,Cy,and p-Tol)or 2-aza-1-metallacyclohexa-2,4,5-triene(R=SiMe_(3))complexes were produced.Mechanistic studies by DFT calculations reveal that 1,2-insertion of the carbodiimide followed by migration of a SiMe_(3) group of the metallacycle occurs for R=iPr,Cy,p-Tol,whereas for R=SiMe_(3) insertion is followed by SiMe_(3) migration along the carbodiimide.The reaction of a 2-aza-1-metallacyclobut-3-ene complex with benzophenone produces a zirconocene amidopyridine complex through a series of unprecedented bond activation and formation events,once again demonstrating the potential of early transition metal complexes for activation and transformation of small molecules.展开更多
Infrared(IR)nonlinear optical(NLO)materials with simultaneous strong NLO coefficient and high laserinduced damaged threshold(LIDT)are the urgently desired optical performance NLO materials in laser application.Here,tw...Infrared(IR)nonlinear optical(NLO)materials with simultaneous strong NLO coefficient and high laserinduced damaged threshold(LIDT)are the urgently desired optical performance NLO materials in laser application.Here,two different electropositive alkali elements are concurrently incorporated into a tetrahedral GaS_(4) anionic framework,affording the first polar quaternary sulphide CsLiGa_(6)S_(10)(CLGS)with mixed ordered alkali cations through the solid-state method.CLGS displays a wide band gap(3.25 eV)originating from the GaS_(4) anionic framework and assistant of the‘dimensional reduction’effect by involving two alkali cations.This merit,accompanied by extremely small anisotropy of the thermal expansion of crystal CLGS(0.05)enhances the LIDT(51.0 MW cm^(2))of 4.5 times that of benchmark AgGaS_(2)(11.3 MW cm^(2))at 1064 nm with the pulse width of 10 ns.Phase CLGS adopts a diamond-like anionic framework in which all tetrahedra are arranged in a highly oriented manner,providing a critical contribution to modest second-harmonic generation 0.7 times that of AgGaS_(2) with a phase-matchable behaviour at the 1910 nm laser.These attributes,along with broad transmittance,warrant the further exploration of potential IR NLO chalcogenides containing multiple alkali cations.展开更多
基金supported by the National Natural Science Foundation of China(no.51432006)the Ministry of Education of China for the Changjiang Innovation Research Team(no.IRT13R24)+1 种基金the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project(no.B13025)the Innovation Program of Shanghai Municipal Education Commission.M.G.H.and C.Z.thank the Australian Research Council for support(DP170100411).
文摘Infrared(IR)nonlinear optical(NLO)materials have attracted tremendous interest for civil and military applications,but it remains a great contemporary challenge to develop high-effciency NLO crystals that possess suffciently high second-harmonic generation(SHG)effciencies coupled to wide transparency ranges and high laser damage thresholds.A series of new hydrous rare-earth iodates RE(IO_(3))_(3)·(H_(2)O)(RE=Y 1,Eu 2)and La_(2)(IO_(3))_(6)(H_(2)O)(3)have been synthesized through facile hydrothermal methods.1 and 2 are isostructural,crystallizing in the polar space group P21,while 3 crystallizes in the polar space group Pc.1-3 feature three-dimensional(3D)frameworks composed of alternately connected corner-shared dis torted[REO_(x)]polyhedra(RE=Y,Eu,and La;x=8,9)and[IO_(3)]^(−)groups.Optical studies showed that 1–3 exhibit good NLO properties,including strong SHG intensities(3.0×(1),4.5×(2),and 1.5×KH_(2)PO_(4)(3)),large band gaps(4.12(1),4.36(2),and 4.24 eV(3),with 2 possessing the largest band gap among the known SHG-active rare-earth-based iodates,high laser damage thresholds(LDT)(53×(1),43×(2),and 44×AgGaS_(2)(3)),and wide transparency ranges(ca.3.0–11.3μm)in the mid-IR region covering two criti cal IR transparency windows;1–3 are therefore potential candidate NLO materials.Density functional theory calculations on 1–3 confirm that their strong SHG responses and large band gaps are mainly derived from the synergistic effect of[IO_(3)]^(−)groups and rare-earth oxide polyhedra[REOx]in their 3D frameworks.We conclude that the introduction of rare-earth cations with moderate electropositivity into iodates may optimize the balance between SHG effciency and optical band gaps,the key requirement for high-performance NLO materials for practical applications.
基金supported by the Research Council of the Shahaid Beheshti University,G.C.of Iran
文摘A hydrodynamic approach is used to investigate a three-component magnetized plasma sheath which consists of electrons and two species of positive ions. Assuming a phase space of one-dimensional spatial coordinate system and three-dimensional velocity coordinate system, the effect of different concentrations of positive ion species on some characteristics of the plasma sheath such as the velocity and density distribution of positive ion species and the electrostatic potential of this region is investigated. The calculated results show that the increase in the density ratio of positive ion species causes a decrease in both the ion velocities and the electrostatic potential of the sheath region. Also, it is shown that in the sheath region of a magnetized plasma consisting of only one positive ion species the bumps of the net density of charged particles disappears much faster. In addition, three-dimensional velocity of each positive ion species in the sheath region is plotted for different concentrations of positive ion species.
基金Financial support by the Deutsche Forschungsgemeinschaft(Project No.452714985)is gratefully acknowledgedfinancial support by the China Scholarship Council(CSC,Grant No.202006380016).
文摘The study of new,unusual structures and reactivity patterns is of great interest for various field of organic and organometallic chemistry.Metallacycles of electropositive transition metals represent an excellent platform for this purpose.In this work,we present the synthesis,characterisation,and reactivity toward carbodiimides of a set of ring-strained group 4 ansa-metallocene-based 1-metallacyclobuta-2,3-dienes Cp’_(2)M(Me_(3)SiC_(3)SiMe_(3))(M=Ti,Zr;Cp’_(2)=indenyl or tetrahydroindenyl based ansa-Cp ligand).In line with experimental studies,computational analysis of the electronic structure of new and previously reported 1-metallacyclobuta-2,3-dienes for the first time shows that the biradical character of these species not only depends on the metal,but also strongly on the nature of the cyclopentadienyl ligands.In reactions with carbodiimides RNvCvNR,depending on the substituents of the carbodiimide,either 2-aza-1-metallacyclobut-3-ene(R=iPr,Cy,and p-Tol)or 2-aza-1-metallacyclohexa-2,4,5-triene(R=SiMe_(3))complexes were produced.Mechanistic studies by DFT calculations reveal that 1,2-insertion of the carbodiimide followed by migration of a SiMe_(3) group of the metallacycle occurs for R=iPr,Cy,p-Tol,whereas for R=SiMe_(3) insertion is followed by SiMe_(3) migration along the carbodiimide.The reaction of a 2-aza-1-metallacyclobut-3-ene complex with benzophenone produces a zirconocene amidopyridine complex through a series of unprecedented bond activation and formation events,once again demonstrating the potential of early transition metal complexes for activation and transformation of small molecules.
基金supported by the National Natural Science Foundation of China(21921001,21827813,92161125,22075283,and 22175172)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2021300)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2020ZZ108,2021ZR205).
文摘Infrared(IR)nonlinear optical(NLO)materials with simultaneous strong NLO coefficient and high laserinduced damaged threshold(LIDT)are the urgently desired optical performance NLO materials in laser application.Here,two different electropositive alkali elements are concurrently incorporated into a tetrahedral GaS_(4) anionic framework,affording the first polar quaternary sulphide CsLiGa_(6)S_(10)(CLGS)with mixed ordered alkali cations through the solid-state method.CLGS displays a wide band gap(3.25 eV)originating from the GaS_(4) anionic framework and assistant of the‘dimensional reduction’effect by involving two alkali cations.This merit,accompanied by extremely small anisotropy of the thermal expansion of crystal CLGS(0.05)enhances the LIDT(51.0 MW cm^(2))of 4.5 times that of benchmark AgGaS_(2)(11.3 MW cm^(2))at 1064 nm with the pulse width of 10 ns.Phase CLGS adopts a diamond-like anionic framework in which all tetrahedra are arranged in a highly oriented manner,providing a critical contribution to modest second-harmonic generation 0.7 times that of AgGaS_(2) with a phase-matchable behaviour at the 1910 nm laser.These attributes,along with broad transmittance,warrant the further exploration of potential IR NLO chalcogenides containing multiple alkali cations.
