Metal(iso)cyanides dominate the molecular inventory of metal-bearing species in the interstellar medium.Their oxide counterparts,metal(iso)cyanates,have potential as interstellar molecules and have received significan...Metal(iso)cyanides dominate the molecular inventory of metal-bearing species in the interstellar medium.Their oxide counterparts,metal(iso)cyanates,have potential as interstellar molecules and have received significant attention.However,cationic complexes HNCOM^(+)as precursors to metal(iso)cyanates are rarely studied.Herein,we investigated HNCOCa^(+)by exploiting infrared spectrometry with isotopic substitutions and quantum chemical calculations.For comparison,the light and heavy alkaline earth metal cationic complexes HNCOBe^(+)and HNCOBa^(+)were also explored.HNCOCa^(+)and HNCOBe^(+)rather than HNCOBa^(+)can be experimentally generated by the reactions of metal cations with HNCO.The observed antisymmetric and symmetric NCO stretching vibrations in HNCOCa^(+)(2362.6 and 1330.4 cm^(−1))are higher than those in free HNCO(2268.5 and 1320.3 cm^(−1))but lower than those in HNCOBe^(+)(2426.4 and 1355.2 cm^(−1)).These shifts can be explained by the charge polarization within the NCO fragment in HNCOBe^(+)and HNCOCa^(+).Bonding analysis suggests that HNCO−Be^(+)bond favors covalent character(54%)while HNCO−Ca^(+)bond has higher electrostatic character(57%).The dominant electrostatic interaction(64%)in HNCO−Ba^(+)bond results in the low bond energy,which might account for its absence in experiments.展开更多
The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-（CH3OH）n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six...The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-（CH3OH）n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six stable luteolin-（CH3OH）2 complexes and four stable luteolin-（CH3OH）3 complexes have been obtained.The theories of atoms in molecules（AIM） and natural bond orbital（NBO） have been used to analyze the hydrogen bonds of these compounds,and their interaction energies corrected by basis set superposition error are between-8.046 and-76.124 kJ/mol.The calculation results indicate strong hydrogen bonding interactions in the luteolin-（CH3OH）n complexes.Then the nuclear magnetic resonance（NMR） and electronic absorption spectrum of luteolin have been calculated,and the results are in agreement with the experimental data.展开更多
The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d,p)and 6-311++G(d,p)basis set by Gaussian program.The results from natural bond orbital(NBO)analysis have been ...The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d,p)and 6-311++G(d,p)basis set by Gaussian program.The results from natural bond orbital(NBO)analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule.The electron density based local reactivity descriptors such as Fukui functions were calculated.The dipole moment(μ)and polarizability(α),anisotropy polarizability(Δα)and first order hyperpolarizability(βtot)of the molecule have been reported.Thermodynamic properties of the title compound were calculated at different temperatures.展开更多
The discovered in 2008 Fe-based superconductors (SC) are a paramagnetic semimetal at ambient temperature and in some cases they become superconductor upon doping. In spite of so many years since its discovery it is st...The discovered in 2008 Fe-based superconductors (SC) are a paramagnetic semimetal at ambient temperature and in some cases they become superconductor upon doping. In spite of so many years since its discovery it is still not known the mechanism that leads to superconductivity. The electronic structure study is used for determining key features of the SC mechanism in these materials. The calculations were performed using the modern suite of programs MOLPRO 2021. We performed quantum calculations of a cluster embedded in a background charge distribution that represents the infinite crystal. The Natural Population Analysis was used for determining the charge and spin distribution in the studied materials. As follows from our results, the possible mechanism for superconductivity corresponds to the RVB theory proposed by Anderson for high T<sub>c</sub> superconductivity in cuprates.展开更多
Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the c...Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the characteristic fragment ions were high in m/z,thereby the interpretation was facilitated.展开更多
In this paper,two types of copper-aluminum heterogeneous electrode plates are stacked and the finite element analysis(FEA)models of two different laser welding conditions are built by using SYSWELD welding simulation ...In this paper,two types of copper-aluminum heterogeneous electrode plates are stacked and the finite element analysis(FEA)models of two different laser welding conditions are built by using SYSWELD welding simulation software to calculate the depth of the welding bead and the temperature distribution of the welding surface.Then,the residual stress analysis data of the welded area are exported and the residual stress is applied to the welded specimen for CAE analysis to ensure that the welding bonding strength meets the design target of a shear force of 500 N or higher.The copper-aluminum laser-stacking simulation technique in this paper can be applied to the manufacturing of copper-aluminum heterogeneous laser-welded electrodes and series-connected electrodes of automotive lithium-ion power battery modules,providing an effective analysis method for welding bonding-strength.展开更多
The magneto-volume effect in Fe-based clusters,as a microscopic manifestation of the Invar effect in Fe-Ni alloys,has recently attracted increasing attention.However,a deeper understanding of the physical mechanism un...The magneto-volume effect in Fe-based clusters,as a microscopic manifestation of the Invar effect in Fe-Ni alloys,has recently attracted increasing attention.However,a deeper understanding of the physical mechanism underlying the magneto-volume effect remains lacking.Here we employed first-principles calculations to investigate the ground-state properties and thermal expansion behaviors of icosahedral Fe_(12)X(X=Ti,Fe,Co,Ni)clusters.The spin arrangement of Fe_(12)X clusters is determined by the magnetic exchange interaction between atomic pairs.During thermal expansion,Fe_(12)X clusters exhibit different volume and magnetic moment behaviors.The magnetic moment attenuation induced by thermal excitation is a prerequisite for the emergence of the magneto-volume effect in Fe_(12)X clusters,consistent with the Invar anomaly observed in Fe-Ni alloys.The bonding characteristic analysis reveals that there are two competing bonding transitions in the process of the moment attenuation.The strengthening of the bonding state of the surface Fe-Fe bonds significantly exceeds the weakening of the bonding state of the Fe-X bonds,resulting in a contraction of the cluster volume,which is considered to be the explanation of the magneto-volume effect at the electronic structure level.Understanding the origin of the magneto-volume effect in magnetic metal clusters not only deepens the insight into the Invar effect but also provides theoretical guidance for its practical application.展开更多
The photodegradation mechanism of fenvalerate in water has been investigated by density functional theory（DFT）.The geometries of reactants,transition states,intermediates and products are optimized at the B3LYP/6-31...The photodegradation mechanism of fenvalerate in water has been investigated by density functional theory（DFT）.The geometries of reactants,transition states,intermediates and products are optimized at the B3LYP/6-31G＊ level.The calculated results indicate that the reaction process mainly includes the nucleophilic attack and the substitution reaction by hydroxyl radical to the carbonyl group.By vibrational frequency analysis and intrinsic reaction coordinate（IRC） method,the transition state and its reaction pathway are confirmed.Moreover,the changes of natural population analysis（NPA）,calculated using the Natural bond orbital（NBO） method,are analyzed along with the degradation reaction which can explain the variation of chemical bonds.Additionally,the solvent effect is also investigated and the results show that the reaction preferably takes place in water.展开更多
Intermolecular interactions between PH2Cl and Ar–R（R = H,OH,NH2,CH3,Br,Cl,F,CN,NO2） were calculated by using MP2/aug-cc-p VDZ quantum chemical method.It has been shown from our calculations that the aromatic rings ...Intermolecular interactions between PH2Cl and Ar–R（R = H,OH,NH2,CH3,Br,Cl,F,CN,NO2） were calculated by using MP2/aug-cc-p VDZ quantum chemical method.It has been shown from our calculations that the aromatic rings with electron-withdrawing groups represent much weaker binding affinities than those with electron-donating groups.The charge-transfer interaction between PH2Cl and Ar–R plays an important role in the formation of pnicogen bond complexes,as revealed by NBO analysis.Nevertheless,AIM analysis shows that the nature of the interactions between PH2Cl and Ar–R is electrostatic,and the interaction energies of the complexes are correlated positively with the electron densities in the bond critical points（BCPs）.RDG/ELF graphical analyses were performed to visualize the positions and strengths of the pnicogen bonding,as well as the spatial change of the electron localization upon the formation of complexes.The π-type halogen bond was also calculated,and it has been revealed that the π-type pnicogen bond systems are more stable than the halogen bond ones.展开更多
In this paper, the reaction mechanism of HOCO with its radical has been investigated deeply by density functional theory（DFT）, while the geometries and harmonic vibration frequencies of the reactants, intermediates,...In this paper, the reaction mechanism of HOCO with its radical has been investigated deeply by density functional theory（DFT）, while the geometries and harmonic vibration frequencies of the reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311＋＋G＊＊ level. The CCSD（T）/cc-p VQZ method was used to further calculate the single-point energy of each stationary point along the reaction channel. The result shows that channels（b） and（d） via carbon-carbon intermediates are competing with the ones（e）,（f）,（i） and（l） through carbon-oxygen intermediates, and the six channels are dominant for the title reaction to produce HCOOH and CO2. The result also indicates that the hydrogen abstraction from the HOCO radical can be performed quickly by the self-interaction of HOCO in the absence of other radicals or atoms, which indirectly proves for the first time that the ground-state cis-HOCO radical is not decomposed by the tunneling effect. In addition, the charges of natural population analysis（NPA） and the variation of chemical bonds have been analyzed by the Natural Bond Orbital（NBO） method along with the important reaction path.展开更多
The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRI...The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.展开更多
Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in catalysis.In this article,the catalytic mechanism and bonding analysis of CO ...Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in catalysis.In this article,the catalytic mechanism and bonding analysis of CO oxidation reaction on bimetallic gold–palladium(Au–Pd)model of single atom alloy Au37Pd1 are investigated by using quantum chemical calculations.The molecular geometries and adsorbate/substrate binding energies of CO@Au–Pd,O2@Au–Pd and CO/O2@Au–Pd configurations are identified.The core-shell structure is confirmed to be the most stable structure for Au–Pd SAA,where the Pd atom prefers to situate at the core site.Charge transfer from the Pd atom to the Au atoms has been confirmed to stabilize the structure.According to the binding energy and chemical bonding analysis,both CO and O2 prefer to bind to the Pd atom at the hex site with low coordination number.The formation of new co-adsorption species is identified,in which vertical and parallel bridging adsorptions of CO and O2 on the Au–Pd bonds are observed.CO oxidation on Au–Pd SAA is found to be feasible with low energy barriers and follows the Langmuir-Hinshewood(L-H)mechanism.Our work offers insights into the significant role of single atom of the SAAs in catalytic reactions and can provide evidence for designing new SAAs with high-performance catalytic activities.展开更多
The article presents an effort to create dimensionless scaling correlations of the overall bed porosity in the case of magnetically assisted fluidization in a tapered vessel with external transverse magnetic field. Th...The article presents an effort to create dimensionless scaling correlations of the overall bed porosity in the case of magnetically assisted fluidization in a tapered vessel with external transverse magnetic field. This is a stand of portion of new branch in the magnetically assisted fluidization recently created concerning employment of tapered vessels. Dimensional analysis based on ＂pressure transform＂ of the initial set of variables and involving the magnetic granular Bond number has been applied to develop scaling relationships of dimensionless groups representing ratios of pressures created by the fluid flow, gravity and the magnetic field over an elementary volume of the fluidized bed. Special attention has been paid on the existing data correlations developed for non-magnetic beds and the links to the new ones especially developed for tapered magnetic counterparts. A special dimensionless variable Xp = （Ar△Dbt）1/3√RgMQ combining Archimedes and Rosensweig numbers has been conceived for porosity correlation. Data correlations have been performed by power-law, exponential decay and asymptotic functions with analysis of their adequacies and accuracies of approximation.展开更多
A theoretical study on the blue-shifted H-bond N-H…O and red-shifted H-bond O-H…O in the complex HNO…H2O2 was conducted by employment of both standard and counterpoise-corrected methods to calculate the geometric s...A theoretical study on the blue-shifted H-bond N-H…O and red-shifted H-bond O-H…O in the complex HNO…H2O2 was conducted by employment of both standard and counterpoise-corrected methods to calculate the geometric structures and vibrational frequencies at the MP2/6-31G（d）, MP2/6-31 ＋ G（d,p）, MP2/6-311 ＋ ＋ G（d,p）, B3LYP/6-31G（d）, B3LYP/6-31 ＋G（d,p） and B3LYP/6-311 ＋ ＋G（d,p） levels. In the H-bond N-H…O, the calculated blue shift of N-H stretching frequency is in the vicinity of 120 cm^-1 and this is indeed the largest theoretical estimate of a blue shift in the X-H…Y H-bond ever reported in the literature. From the natural bond orbital analysis, the red-shifted H-bond O-H…O can be explained on the basis of the dominant role of the hyperconjugation. For the blue-shifted H-bond N-H…O, the hyperconjugation was inhibited due to the existence of significant electron density redistribution effect, and the large blue shift of the N-H stretching frequency was prominently due to the rehybridization of spn N-H hybrid orbital.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.22025301,No.22273012,and No.22321003).
文摘Metal(iso)cyanides dominate the molecular inventory of metal-bearing species in the interstellar medium.Their oxide counterparts,metal(iso)cyanates,have potential as interstellar molecules and have received significant attention.However,cationic complexes HNCOM^(+)as precursors to metal(iso)cyanates are rarely studied.Herein,we investigated HNCOCa^(+)by exploiting infrared spectrometry with isotopic substitutions and quantum chemical calculations.For comparison,the light and heavy alkaline earth metal cationic complexes HNCOBe^(+)and HNCOBa^(+)were also explored.HNCOCa^(+)and HNCOBe^(+)rather than HNCOBa^(+)can be experimentally generated by the reactions of metal cations with HNCO.The observed antisymmetric and symmetric NCO stretching vibrations in HNCOCa^(+)(2362.6 and 1330.4 cm^(−1))are higher than those in free HNCO(2268.5 and 1320.3 cm^(−1))but lower than those in HNCOBe^(+)(2426.4 and 1355.2 cm^(−1)).These shifts can be explained by the charge polarization within the NCO fragment in HNCOBe^(+)and HNCOCa^(+).Bonding analysis suggests that HNCO−Be^(+)bond favors covalent character(54%)while HNCO−Ca^(+)bond has higher electrostatic character(57%).The dominant electrostatic interaction(64%)in HNCO−Ba^(+)bond results in the low bond energy,which might account for its absence in experiments.
文摘The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-（CH3OH）n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six stable luteolin-（CH3OH）2 complexes and four stable luteolin-（CH3OH）3 complexes have been obtained.The theories of atoms in molecules（AIM） and natural bond orbital（NBO） have been used to analyze the hydrogen bonds of these compounds,and their interaction energies corrected by basis set superposition error are between-8.046 and-76.124 kJ/mol.The calculation results indicate strong hydrogen bonding interactions in the luteolin-（CH3OH）n complexes.Then the nuclear magnetic resonance（NMR） and electronic absorption spectrum of luteolin have been calculated,and the results are in agreement with the experimental data.
文摘The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d,p)and 6-311++G(d,p)basis set by Gaussian program.The results from natural bond orbital(NBO)analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule.The electron density based local reactivity descriptors such as Fukui functions were calculated.The dipole moment(μ)and polarizability(α),anisotropy polarizability(Δα)and first order hyperpolarizability(βtot)of the molecule have been reported.Thermodynamic properties of the title compound were calculated at different temperatures.
文摘The discovered in 2008 Fe-based superconductors (SC) are a paramagnetic semimetal at ambient temperature and in some cases they become superconductor upon doping. In spite of so many years since its discovery it is still not known the mechanism that leads to superconductivity. The electronic structure study is used for determining key features of the SC mechanism in these materials. The calculations were performed using the modern suite of programs MOLPRO 2021. We performed quantum calculations of a cluster embedded in a background charge distribution that represents the infinite crystal. The Natural Population Analysis was used for determining the charge and spin distribution in the studied materials. As follows from our results, the possible mechanism for superconductivity corresponds to the RVB theory proposed by Anderson for high T<sub>c</sub> superconductivity in cuprates.
文摘Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the characteristic fragment ions were high in m/z,thereby the interpretation was facilitated.
基金sponsored by the MOEA(Ministry of Economic Affairs)from the Technology Development Program No.109-EC-17-A-25-1581。
文摘In this paper,two types of copper-aluminum heterogeneous electrode plates are stacked and the finite element analysis(FEA)models of two different laser welding conditions are built by using SYSWELD welding simulation software to calculate the depth of the welding bead and the temperature distribution of the welding surface.Then,the residual stress analysis data of the welded area are exported and the residual stress is applied to the welded specimen for CAE analysis to ensure that the welding bonding strength meets the design target of a shear force of 500 N or higher.The copper-aluminum laser-stacking simulation technique in this paper can be applied to the manufacturing of copper-aluminum heterogeneous laser-welded electrodes and series-connected electrodes of automotive lithium-ion power battery modules,providing an effective analysis method for welding bonding-strength.
基金financially supported by the National Natural Science Foundation of China(No.52171038)the Key Technology Research and Development Program of Shandong Province(Nos.2021SFGC1001 and 2023CXGC010403)+2 种基金the program of Jinan Science and Technology Bureau(No.2020GXRC019)key projects for serving Shandong Province(No.31370004012207)the National Key Research and Development Program of China(No.2023YFB3712600).
文摘The magneto-volume effect in Fe-based clusters,as a microscopic manifestation of the Invar effect in Fe-Ni alloys,has recently attracted increasing attention.However,a deeper understanding of the physical mechanism underlying the magneto-volume effect remains lacking.Here we employed first-principles calculations to investigate the ground-state properties and thermal expansion behaviors of icosahedral Fe_(12)X(X=Ti,Fe,Co,Ni)clusters.The spin arrangement of Fe_(12)X clusters is determined by the magnetic exchange interaction between atomic pairs.During thermal expansion,Fe_(12)X clusters exhibit different volume and magnetic moment behaviors.The magnetic moment attenuation induced by thermal excitation is a prerequisite for the emergence of the magneto-volume effect in Fe_(12)X clusters,consistent with the Invar anomaly observed in Fe-Ni alloys.The bonding characteristic analysis reveals that there are two competing bonding transitions in the process of the moment attenuation.The strengthening of the bonding state of the surface Fe-Fe bonds significantly exceeds the weakening of the bonding state of the Fe-X bonds,resulting in a contraction of the cluster volume,which is considered to be the explanation of the magneto-volume effect at the electronic structure level.Understanding the origin of the magneto-volume effect in magnetic metal clusters not only deepens the insight into the Invar effect but also provides theoretical guidance for its practical application.
基金supported by the National Natural Science Foundation of China (Nos.40976041 and 20775074)
文摘The photodegradation mechanism of fenvalerate in water has been investigated by density functional theory（DFT）.The geometries of reactants,transition states,intermediates and products are optimized at the B3LYP/6-31G＊ level.The calculated results indicate that the reaction process mainly includes the nucleophilic attack and the substitution reaction by hydroxyl radical to the carbonyl group.By vibrational frequency analysis and intrinsic reaction coordinate（IRC） method,the transition state and its reaction pathway are confirmed.Moreover,the changes of natural population analysis（NPA）,calculated using the Natural bond orbital（NBO） method,are analyzed along with the degradation reaction which can explain the variation of chemical bonds.Additionally,the solvent effect is also investigated and the results show that the reaction preferably takes place in water.
基金Supported by the Science and Technology Project of Zhejiang Province(2016C33039)Natural Science Foundation of Zhejiang Province(LY14C030004)+2 种基金National Natural Science Foundation of China(21272211)Project of the Special Foundation for Provincial Research Institutes of Zhejiang Province,China(2017F50002)Science and Technology Planning Project of the Zhejiang Provincial Department of Water Resources(RB1608)
文摘Intermolecular interactions between PH2Cl and Ar–R（R = H,OH,NH2,CH3,Br,Cl,F,CN,NO2） were calculated by using MP2/aug-cc-p VDZ quantum chemical method.It has been shown from our calculations that the aromatic rings with electron-withdrawing groups represent much weaker binding affinities than those with electron-donating groups.The charge-transfer interaction between PH2Cl and Ar–R plays an important role in the formation of pnicogen bond complexes,as revealed by NBO analysis.Nevertheless,AIM analysis shows that the nature of the interactions between PH2Cl and Ar–R is electrostatic,and the interaction energies of the complexes are correlated positively with the electron densities in the bond critical points（BCPs）.RDG/ELF graphical analyses were performed to visualize the positions and strengths of the pnicogen bonding,as well as the spatial change of the electron localization upon the formation of complexes.The π-type halogen bond was also calculated,and it has been revealed that the π-type pnicogen bond systems are more stable than the halogen bond ones.
基金supported by the National Natural Science Foundation of China(50673085,20677053)the Basic Research Programs of Qingdao Science and Technology Plan(No.13-1-4-233-jch)
文摘In this paper, the reaction mechanism of HOCO with its radical has been investigated deeply by density functional theory（DFT）, while the geometries and harmonic vibration frequencies of the reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311＋＋G＊＊ level. The CCSD（T）/cc-p VQZ method was used to further calculate the single-point energy of each stationary point along the reaction channel. The result shows that channels（b） and（d） via carbon-carbon intermediates are competing with the ones（e）,（f）,（i） and（l） through carbon-oxygen intermediates, and the six channels are dominant for the title reaction to produce HCOOH and CO2. The result also indicates that the hydrogen abstraction from the HOCO radical can be performed quickly by the self-interaction of HOCO in the absence of other radicals or atoms, which indirectly proves for the first time that the ground-state cis-HOCO radical is not decomposed by the tunneling effect. In addition, the charges of natural population analysis（NPA） and the variation of chemical bonds have been analyzed by the Natural Bond Orbital（NBO） method along with the important reaction path.
基金gratefully acknowledge the Dalian Coherent Light Source(DCLS)for support and assistanceThis work was supported by the National Natural Science Foundation of China(No.22288201)+1 种基金the Chinese Academy of Sciences(GJJSTD20220001)the Innovation Program for Quantum Science and Technology(No.2021ZD0303305).
文摘The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.
基金supported by the National Natural Science Foundation of China (91645203,21433005,and 21590792)the Tsinghua Xuetang Talents Program for providing computational resources+1 种基金the support from DGAPA-UNAM (IN108817)Conacyt-Mexico (285821)
文摘Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in catalysis.In this article,the catalytic mechanism and bonding analysis of CO oxidation reaction on bimetallic gold–palladium(Au–Pd)model of single atom alloy Au37Pd1 are investigated by using quantum chemical calculations.The molecular geometries and adsorbate/substrate binding energies of CO@Au–Pd,O2@Au–Pd and CO/O2@Au–Pd configurations are identified.The core-shell structure is confirmed to be the most stable structure for Au–Pd SAA,where the Pd atom prefers to situate at the core site.Charge transfer from the Pd atom to the Au atoms has been confirmed to stabilize the structure.According to the binding energy and chemical bonding analysis,both CO and O2 prefer to bind to the Pd atom at the hex site with low coordination number.The formation of new co-adsorption species is identified,in which vertical and parallel bridging adsorptions of CO and O2 on the Au–Pd bonds are observed.CO oxidation on Au–Pd SAA is found to be feasible with low energy barriers and follows the Langmuir-Hinshewood(L-H)mechanism.Our work offers insights into the significant role of single atom of the SAAs in catalytic reactions and can provide evidence for designing new SAAs with high-performance catalytic activities.
文摘The article presents an effort to create dimensionless scaling correlations of the overall bed porosity in the case of magnetically assisted fluidization in a tapered vessel with external transverse magnetic field. This is a stand of portion of new branch in the magnetically assisted fluidization recently created concerning employment of tapered vessels. Dimensional analysis based on ＂pressure transform＂ of the initial set of variables and involving the magnetic granular Bond number has been applied to develop scaling relationships of dimensionless groups representing ratios of pressures created by the fluid flow, gravity and the magnetic field over an elementary volume of the fluidized bed. Special attention has been paid on the existing data correlations developed for non-magnetic beds and the links to the new ones especially developed for tapered magnetic counterparts. A special dimensionless variable Xp = （Ar△Dbt）1/3√RgMQ combining Archimedes and Rosensweig numbers has been conceived for porosity correlation. Data correlations have been performed by power-law, exponential decay and asymptotic functions with analysis of their adequacies and accuracies of approximation.
基金Project supported by the National Natural Science Foundation of China （No. G20477043） and Knowledge Creative Program of Chinese Academy of Sciences （No. KJCX2-SW-H08）.
文摘A theoretical study on the blue-shifted H-bond N-H…O and red-shifted H-bond O-H…O in the complex HNO…H2O2 was conducted by employment of both standard and counterpoise-corrected methods to calculate the geometric structures and vibrational frequencies at the MP2/6-31G（d）, MP2/6-31 ＋ G（d,p）, MP2/6-311 ＋ ＋ G（d,p）, B3LYP/6-31G（d）, B3LYP/6-31 ＋G（d,p） and B3LYP/6-311 ＋ ＋G（d,p） levels. In the H-bond N-H…O, the calculated blue shift of N-H stretching frequency is in the vicinity of 120 cm^-1 and this is indeed the largest theoretical estimate of a blue shift in the X-H…Y H-bond ever reported in the literature. From the natural bond orbital analysis, the red-shifted H-bond O-H…O can be explained on the basis of the dominant role of the hyperconjugation. For the blue-shifted H-bond N-H…O, the hyperconjugation was inhibited due to the existence of significant electron density redistribution effect, and the large blue shift of the N-H stretching frequency was prominently due to the rehybridization of spn N-H hybrid orbital.
