The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3+ ions selectively located in Ta and Na sites, respectiv...The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3+ ions selectively located in Ta and Na sites, respectively, the band gaps of two Eu-doped NaTaO3 models were all narrowed, which were assigned to lattice defects and impurity band of the Eu dopent. For the model of Eu3+ ions located in the Na+ sites of NaTaO3, the new impurity band mainly composited of Eu 4f orbital appeared at the top over the valence band, indicating the enhanced oxidative ability. For the model of Eu3+ ions located in the Ta5+ sites of NaTaO3, a midgap state generated was located at the bottom of conduct band and the band potential shifted up, confirming the strong reductive ability in the Na-rich enviornment. The densities of electron states were significantly increased in both the conduction and valence bands in Na-rich model, which resulted in the increased carrier migration rate and thus photocatalytic activity enhancement. It is proposed that Eu3+ ions doping at the Ta sites could enhance the reduced photocatalytic performance via controlling the nonstoichiometric Na/Ta molar ratio in the Eu-doped NaTaO3 system.展开更多
Comprehensive Summary The experimental investigation of rare-earth metal-metal bonds remains a challenge in the study of chemical bonds.Herein,we report the synthesis and characterization of a novel heteronuclear di-m...Comprehensive Summary The experimental investigation of rare-earth metal-metal bonds remains a challenge in the study of chemical bonds.Herein,we report the synthesis and characterization of a novel heteronuclear di-metallofullerene,ScY@C_(3v)(8)-C_(82),which contains a mixed rare-earth metal-metal bond.ScY@C_(3v)(8)-C_(82)was successfully synthesized by arc-discharging method and characterized by mass spectrometry,UV-vis-NIR spectroscopy and single-crystal X-ray diffraction crystallography,which unambiguously determined its molecular structure.Theoretical calculations were also performed to study the optimized positions of Sc-Y metallic dimer and the electronic configuration.The combined experimental and theoretical results confirmed that both Sc and Y atoms transfer two electrons to the C_(3v)(8)-C_(82)cage,i.e.,(ScY)4+@(C_(3v)(8)-C_(82))4-.In particular,a covalent Sc-Yσ2 bond,which has never been reported before,is proven to be formed inside C_(3v)(8)-C_(82)fullerene cage.This work presents a novel di-metallofullerene containing mixed rare-earth metal-metal bond and expands the understanding of metal-metal bonding of rare earth elements.展开更多
Electrochemical nitrogen reduction reaction(NRR)is a mild and sustainable method for ammonia synthesis.Therefore,developing high activity,selectivity,and economic efficiency catalysts with considering the synergistic ...Electrochemical nitrogen reduction reaction(NRR)is a mild and sustainable method for ammonia synthesis.Therefore,developing high activity,selectivity,and economic efficiency catalysts with considering the synergistic effects between catalysts and carriers to design novel structural models is very important.Considering the non-noble metal NRR catalyst,Mo3,we tried to find a suitable carrier which is stable and economical.Herein,we used the largest atomically precise aluminum-pyrazole ring(AlOC-69)to date(diameter up to 2.3 nm).The larger ring cavities and the presence of abundant hydroxy groups make AlOC-69 an ideal molecular carrier model and provide a basis for studying its structure-activity relationship.The formation energy(-0.76eV)and stable Mo-0 bonds indicate that Mo_(3)can be stabilized on the Al_(10)O_(10)surface.Additionally,N_(2)has fully activated due to the strong interaction between the p-orbital of N and the d-orbital of Mo.The low limiting potential(-0.28V)emerges that Mo_(3)@Al_(10)O_(10)has ideal catalytic activity and selectivity.This research provides a promising catalyst model and an understanding of its catalytic process at the atomic level,providing a new approach for the co-design of catalyst and carrierin NRR.展开更多
Large eddy simulations (LES) have been performed to investigate the flow and combustion fields in the scramjet of the German Aerospace Center (DLR). Turbulent combustion is mod- eled by the tabulated thermo-chemis...Large eddy simulations (LES) have been performed to investigate the flow and combustion fields in the scramjet of the German Aerospace Center (DLR). Turbulent combustion is mod- eled by the tabulated thermo-chemistry approach in combination with the presumed probability density function (PDF). A/3-function is used to model the distribution of the mixture fraction, while two different PDFs, g-function (Model I) and //-function (Model II), are applied to model the reaction progress. Temperature is obtained by solving filtered energy transport equation and the reaction rate of the progress variable is rescaled by pressure to consider the effects of compressibil- ity. The adaptive mesh refinement (AMR) technique is used to properly capture shock waves, boundary layers, shear layers and flame structures. Statistical results of temperature and velocity predicted by Model II show better accuracy than that predicted by Model I. The results of scatter points and mixture fraction-conditional variables indicate the significant differences between Model I and Model II. It is concluded that second moment information in the presumed PDF of the reaction progress is very important in the simulation of supersonic combustion. It is also found that an unstable flame with extinction and ignition develops in the shear layers of bluff body and a fuel- rich partially premixed flame stabilizes in the central recirculation bubble.展开更多
The adduct reaction paths for GaN growth by metal organic chemical vapor deposition (MOCVD) were studied by quantum chemical calculations employing density functional theory (DFT). Five possible adduct reaction paths ...The adduct reaction paths for GaN growth by metal organic chemical vapor deposition (MOCVD) were studied by quantum chemical calculations employing density functional theory (DFT). Five possible adduct reaction paths with or without the ex-cess NH3were proposed and the corresponding potential energy surfaces were calculated. From the calculation results, it is concluded that after the formation of DMGNH2from TMG:NH3, the further decomposition paths have very slim probability because of the high energy barriers; whereas the oligomerization pathway to form oligomers [DMGNH2]x(x=2, 3) is probable,because of zero energy barrier. Since the oligomers tend to further polymerize, the nanoparticles are easily formed through this path. When NH3is in excess, TMG:NH3 tends to combine with the second NH3to form two new complexes: the coordination-bonded compound H3N:TMG:NH3and the hydrogen-bonded compound TMG:NH3 NH3. The formation of hydrogen-bonded compound TMG:NH3 NH3 will be more probable because of the lower energy than H3N:TMG:NH3. By comparing the potential energy surfaces in five adduct reaction paths, we postulate that, under the growth conditions of GaN MOCVD, the formation of hydrogen-bonded compound TMG:NH3 NH3 followed by the reversible decomposition may be the main reaction path for GaN thin film growth; while the adduct oligomerization path to generate oligomers [DMGNH2]2 and [DMGNH2]3might be the main reaction path for nanoparticles formation.展开更多
The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density function...The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory (DFT) method. Twelve possible support models of regular and defective MgC12 (110) and (100) surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate (EB) as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TIC14 from coordinating on the MgC12 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgC12 support, presented stronger adsorption of TiCl4 than that of EB on (110) surface. Since the TIC14 and ethyl benzoate (EB) would compete to adsorb on the support surface, it seems reasonable to assume that TIC14 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.展开更多
The structures and second-order nonlinear optical (NLO) properties of a series of chlorobenzyl-o-carboranes derivatives (1 12) containing different push-pull groups have been studied by density functional theory ...The structures and second-order nonlinear optical (NLO) properties of a series of chlorobenzyl-o-carboranes derivatives (1 12) containing different push-pull groups have been studied by density functional theory (DFT) cal- culation. Our theoretical calculations show that the static first hyperpolarizability (fltot) values gradually increase with increasing the π-conjugation length and the strength of electron donor group. Especially, compound 12 exhibits the largest βtot (62.404 × 10^-30 esu) by introducing tetrathiafulvalene (TTF), which is about 76 times larger than that of compound 1 containing aryl. This means that the appropriate structural modification can substantially increase the first hyperpolarizabilities of the studied compounds. For the sake of understanding the origin of these large NLO responses, the frontier molecular orbitals (FMOs), electron density difference maps (EDDMs), orbital energy and electronic transition energy of the studied compounds are analyzed. According to the two-state model, the lower transition energy plays an important role in increasing the first hyperpolarizability values. This study may evoke possible ways to design preferable NLO materials.展开更多
Carbolong compounds as a metal-heteroaromatic compound with both organometallic properties andπ-conjugated systems exhibit great potential in organic catalysis and optoelectronic devices.In this work,for the first ti...Carbolong compounds as a metal-heteroaromatic compound with both organometallic properties andπ-conjugated systems exhibit great potential in organic catalysis and optoelectronic devices.In this work,for the first time,the“Bucket Effect”is revealed to promote the third-order nonlinear optical(NLO)performance in metal-heteroaromatic compounds.We have successfully constructed and investigated a series of novel metallapentalenes with higher third-order NLO performance benefited from the“Bucket Effect”.Meanwhile,aromaticity and electron−hole analysis further confirm the internal homogeneity of organometallic rings,reduced bandgap,and enhanced low-energy peak response resulted in the enhanced third-order NLO effects.The success of this work is discovering an emerging material library of high third-order NLO effects,and illustrating the feasibility of engineering the high response metal-heteroaromatic optical devices at the electronic structure level.展开更多
Cathode materials are the most critical chal- lenge for the large scale application of Li-ion batteries in electric vehicles and for the storages of electricity. The first principles calculations play an important rol...Cathode materials are the most critical chal- lenge for the large scale application of Li-ion batteries in electric vehicles and for the storages of electricity. The first principles calculations play an important role in develop- ment and optimization of novel cathode materials. In this paper, we overview the first principles calculations of energy, volume change, band-gap, phase diagram, and Li- ion transport mechanism of cathode materials with an emphasis on the design of such materials. We also over- view the recent progress of data mining techniques and the high-throughput first principles calculations for the design and development of cathode materials. Finally, we preview the challenges and opportunities of this rapidly developing field.展开更多
基金Financially supported by the National Natural Science Foundation of China(No.21267014 and 21567017)
文摘The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3+ ions selectively located in Ta and Na sites, respectively, the band gaps of two Eu-doped NaTaO3 models were all narrowed, which were assigned to lattice defects and impurity band of the Eu dopent. For the model of Eu3+ ions located in the Na+ sites of NaTaO3, the new impurity band mainly composited of Eu 4f orbital appeared at the top over the valence band, indicating the enhanced oxidative ability. For the model of Eu3+ ions located in the Ta5+ sites of NaTaO3, a midgap state generated was located at the bottom of conduct band and the band potential shifted up, confirming the strong reductive ability in the Na-rich enviornment. The densities of electron states were significantly increased in both the conduction and valence bands in Na-rich model, which resulted in the increased carrier migration rate and thus photocatalytic activity enhancement. It is proposed that Eu3+ ions doping at the Ta sites could enhance the reduced photocatalytic performance via controlling the nonstoichiometric Na/Ta molar ratio in the Eu-doped NaTaO3 system.
基金the National Science Foundation China(NSFC No.52172051)the NSF of Jiangsu Province(BK20200041)+2 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)A.R.-F.and J.M.P.thank the Spanish Ministry of Science(grant PID2020-112762GB-I00 funded by MCIN/AEl/10.13039/501100011033)the Generalitat de Catalunya(grant 2021 SGR 00110)and the URV for support.
文摘Comprehensive Summary The experimental investigation of rare-earth metal-metal bonds remains a challenge in the study of chemical bonds.Herein,we report the synthesis and characterization of a novel heteronuclear di-metallofullerene,ScY@C_(3v)(8)-C_(82),which contains a mixed rare-earth metal-metal bond.ScY@C_(3v)(8)-C_(82)was successfully synthesized by arc-discharging method and characterized by mass spectrometry,UV-vis-NIR spectroscopy and single-crystal X-ray diffraction crystallography,which unambiguously determined its molecular structure.Theoretical calculations were also performed to study the optimized positions of Sc-Y metallic dimer and the electronic configuration.The combined experimental and theoretical results confirmed that both Sc and Y atoms transfer two electrons to the C_(3v)(8)-C_(82)cage,i.e.,(ScY)4+@(C_(3v)(8)-C_(82))4-.In particular,a covalent Sc-Yσ2 bond,which has never been reported before,is proven to be formed inside C_(3v)(8)-C_(82)fullerene cage.This work presents a novel di-metallofullerene containing mixed rare-earth metal-metal bond and expands the understanding of metal-metal bonding of rare earth elements.
基金supported by the National Natural Science Foundation of China(Nos.92161105 and 92061104)Natural Science Foundation of Fujian Province(Nos.2021j06035 and 2021J01525)Youth Innovation Promotion Association CAS(No.Y2021081).
文摘Electrochemical nitrogen reduction reaction(NRR)is a mild and sustainable method for ammonia synthesis.Therefore,developing high activity,selectivity,and economic efficiency catalysts with considering the synergistic effects between catalysts and carriers to design novel structural models is very important.Considering the non-noble metal NRR catalyst,Mo3,we tried to find a suitable carrier which is stable and economical.Herein,we used the largest atomically precise aluminum-pyrazole ring(AlOC-69)to date(diameter up to 2.3 nm).The larger ring cavities and the presence of abundant hydroxy groups make AlOC-69 an ideal molecular carrier model and provide a basis for studying its structure-activity relationship.The formation energy(-0.76eV)and stable Mo-0 bonds indicate that Mo_(3)can be stabilized on the Al_(10)O_(10)surface.Additionally,N_(2)has fully activated due to the strong interaction between the p-orbital of N and the d-orbital of Mo.The low limiting potential(-0.28V)emerges that Mo_(3)@Al_(10)O_(10)has ideal catalytic activity and selectivity.This research provides a promising catalyst model and an understanding of its catalytic process at the atomic level,providing a new approach for the co-design of catalyst and carrierin NRR.
基金financial support by the National Natural Science Foundation of China (Nos. 51176178, 50936005)
文摘Large eddy simulations (LES) have been performed to investigate the flow and combustion fields in the scramjet of the German Aerospace Center (DLR). Turbulent combustion is mod- eled by the tabulated thermo-chemistry approach in combination with the presumed probability density function (PDF). A/3-function is used to model the distribution of the mixture fraction, while two different PDFs, g-function (Model I) and //-function (Model II), are applied to model the reaction progress. Temperature is obtained by solving filtered energy transport equation and the reaction rate of the progress variable is rescaled by pressure to consider the effects of compressibil- ity. The adaptive mesh refinement (AMR) technique is used to properly capture shock waves, boundary layers, shear layers and flame structures. Statistical results of temperature and velocity predicted by Model II show better accuracy than that predicted by Model I. The results of scatter points and mixture fraction-conditional variables indicate the significant differences between Model I and Model II. It is concluded that second moment information in the presumed PDF of the reaction progress is very important in the simulation of supersonic combustion. It is also found that an unstable flame with extinction and ignition develops in the shear layers of bluff body and a fuel- rich partially premixed flame stabilizes in the central recirculation bubble.
基金supported by the National Natural Science Foundation of China (Grant No. 61176009)
文摘The adduct reaction paths for GaN growth by metal organic chemical vapor deposition (MOCVD) were studied by quantum chemical calculations employing density functional theory (DFT). Five possible adduct reaction paths with or without the ex-cess NH3were proposed and the corresponding potential energy surfaces were calculated. From the calculation results, it is concluded that after the formation of DMGNH2from TMG:NH3, the further decomposition paths have very slim probability because of the high energy barriers; whereas the oligomerization pathway to form oligomers [DMGNH2]x(x=2, 3) is probable,because of zero energy barrier. Since the oligomers tend to further polymerize, the nanoparticles are easily formed through this path. When NH3is in excess, TMG:NH3 tends to combine with the second NH3to form two new complexes: the coordination-bonded compound H3N:TMG:NH3and the hydrogen-bonded compound TMG:NH3 NH3. The formation of hydrogen-bonded compound TMG:NH3 NH3 will be more probable because of the lower energy than H3N:TMG:NH3. By comparing the potential energy surfaces in five adduct reaction paths, we postulate that, under the growth conditions of GaN MOCVD, the formation of hydrogen-bonded compound TMG:NH3 NH3 followed by the reversible decomposition may be the main reaction path for GaN thin film growth; while the adduct oligomerization path to generate oligomers [DMGNH2]2 and [DMGNH2]3might be the main reaction path for nanoparticles formation.
基金supported by the Program of Introducing Talents of Discipline to Universities (B08021)Fundamental Research Funds for the Central Universities
文摘The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory (DFT) method. Twelve possible support models of regular and defective MgC12 (110) and (100) surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate (EB) as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TIC14 from coordinating on the MgC12 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgC12 support, presented stronger adsorption of TiCl4 than that of EB on (110) surface. Since the TIC14 and ethyl benzoate (EB) would compete to adsorb on the support surface, it seems reasonable to assume that TIC14 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.
文摘The structures and second-order nonlinear optical (NLO) properties of a series of chlorobenzyl-o-carboranes derivatives (1 12) containing different push-pull groups have been studied by density functional theory (DFT) cal- culation. Our theoretical calculations show that the static first hyperpolarizability (fltot) values gradually increase with increasing the π-conjugation length and the strength of electron donor group. Especially, compound 12 exhibits the largest βtot (62.404 × 10^-30 esu) by introducing tetrathiafulvalene (TTF), which is about 76 times larger than that of compound 1 containing aryl. This means that the appropriate structural modification can substantially increase the first hyperpolarizabilities of the studied compounds. For the sake of understanding the origin of these large NLO responses, the frontier molecular orbitals (FMOs), electron density difference maps (EDDMs), orbital energy and electronic transition energy of the studied compounds are analyzed. According to the two-state model, the lower transition energy plays an important role in increasing the first hyperpolarizability values. This study may evoke possible ways to design preferable NLO materials.
基金supported by the National Natural Science Foundation of China(No.92161105).
文摘Carbolong compounds as a metal-heteroaromatic compound with both organometallic properties andπ-conjugated systems exhibit great potential in organic catalysis and optoelectronic devices.In this work,for the first time,the“Bucket Effect”is revealed to promote the third-order nonlinear optical(NLO)performance in metal-heteroaromatic compounds.We have successfully constructed and investigated a series of novel metallapentalenes with higher third-order NLO performance benefited from the“Bucket Effect”.Meanwhile,aromaticity and electron−hole analysis further confirm the internal homogeneity of organometallic rings,reduced bandgap,and enhanced low-energy peak response resulted in the enhanced third-order NLO effects.The success of this work is discovering an emerging material library of high third-order NLO effects,and illustrating the feasibility of engineering the high response metal-heteroaromatic optical devices at the electronic structure level.
基金the National Natural Science Foundation of China(Grant Nos.21073118,21376147)the Innovation Program of Shanghai Municipal Education Commission (Grant No.13ZZ078)the 085 Knowledge Innovation Program for the financial support
文摘Cathode materials are the most critical chal- lenge for the large scale application of Li-ion batteries in electric vehicles and for the storages of electricity. The first principles calculations play an important role in develop- ment and optimization of novel cathode materials. In this paper, we overview the first principles calculations of energy, volume change, band-gap, phase diagram, and Li- ion transport mechanism of cathode materials with an emphasis on the design of such materials. We also over- view the recent progress of data mining techniques and the high-throughput first principles calculations for the design and development of cathode materials. Finally, we preview the challenges and opportunities of this rapidly developing field.