The spin crossover（SCO） compound [Fe（bapbpy）（NCS）2],where bapbpy contains two fused N,N-bis（2-pyridyl）amines,has been studied by DFT/TD-DFT/BS-DFT methods.Several density functionals and basis sets were used i...The spin crossover（SCO） compound [Fe（bapbpy）（NCS）2],where bapbpy contains two fused N,N-bis（2-pyridyl）amines,has been studied by DFT/TD-DFT/BS-DFT methods.Several density functionals and basis sets were used in the calculation to obtain optimized geometries of the compound in the low-（LS） and high-spin（HS） states.The vibrational modes and IR spectra,spin splitting energies,excited states and UV/Vis absorption spectra were obtained.The structural parameters of the calculated isolated complex are in good agreement with the X-ray data.We investigate three dimers of [Fe（bapbpy）（NCS）2] complex for their magnetic properties.It has been found that the complex（1,3） has ferromagnetic character while the others are antiferromagnetic in nature by using a broken symmetry approach in the DFT framework（BS-DFT） with support from the coupling constant values（J） and spin density plots.展开更多
Based on density functional theory(DFT) and time-dependent density functional theory(TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer(ESIPT) process and photophysical properties ...Based on density functional theory(DFT) and time-dependent density functional theory(TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer(ESIPT) process and photophysical properties of 2-(2’-hydroxyphenyl)-4-chloromethylthiazole(HCT) are studied. The electron-donating group(CH_(3), OH) and electronwithdrawing group(CF_(3), CHO) are introduced to analyze the changes of intramolecular H-bond, the frontier molecular orbitals, the absorption/fluorescence spectra, and the energy barrier of ESIPT process. The calculation results indicate that electron-donating group strengthens the intramolecular H-bond in the S_(1) state, and leads to an easier ESIPT process. The electron-withdrawing group weakens the corresponding H-bond and makes ESIPT process a little harder. Different substituents also affect the photophysical properties of HCT. The electron-withdrawing group(CF_(3), CHO) has a little effect on electronic spectra. The electron-donating group(CH_(3), OH) red-shifts both the absorption and fluorescence emission peaks of HCT, respectively, which causes the Stokes shift to increase.展开更多
A charge transfer hydrogen bonded complex between the electron donor (proton acceptor) 2-amino-4,6-dimethylpyridine with the electron acceptor (proton donor) chloranilic acid has been synthesized and studied experimen...A charge transfer hydrogen bonded complex between the electron donor (proton acceptor) 2-amino-4,6-dimethylpyridine with the electron acceptor (proton donor) chloranilic acid has been synthesized and studied experimentally and theoretically. The stability constant recorded high values indicating the high stability of the formed complex. In chloroform, ethanol, methanol and acetonitrile were found the stoichiometric ratio 1:1. The solid complex was prepared and characterized by different spectroscopy techniques. FTIR, 1H and 13C NMR studies supported the presence of proton and charge transfers in the formed complex. Complemented with experimental results, molecular modelling using the density functional theory (DFT) calculations was carried out in the gas, chloroform and methanol phases where the existence of charge and hydrogen transfers. Finally, a good consistency between experimental and theoretical calculations was found confirming that the applied basis set is the suitable one for the system under investigation.展开更多
Benzothiazole (BTH) and its derivatives are organic molecules with biologic actions. Because of their many applications, they are produced on a massive scale and used in a number of environmental compartments. Their d...Benzothiazole (BTH) and its derivatives are organic molecules with biologic actions. Because of their many applications, they are produced on a massive scale and used in a number of environmental compartments. Their discharge into water produces environmental problems, exposing our environment to public health problems. A solution that can contribute to their deterioration is becoming a necessity. For this reason, a conceptual analysis of the reactivity of benzothiazole and four of its compounds was undertaken in order to investigate certain aspects of their biodegradability. A theoretical investigations of the compounds studied were conducted in the gas and water phases with the most widely used density functional theory method, Becke-3-Parameter-Lee-Yang-Parr (B3LYP) with 6-31G+ (d, p) basis. Reactivity study calculated global indices of reactivity revealed that 2-SCH3_BTH is the most reactive. Dipole moment values analysis reveals that 2-NH2_BTH is the most soluble in water, while the lipophilicity shows that 2-NH2_BTH is the most hydrophilic compound. Thermodynamic parameters values reflect that reactions are respectively exothermic and spontaneous. By analyzing an Electrostatic Molecular Potential (EMP) map, researchers can pinpoint reactive sites on a molecule and anticipate its reactivity. This assessment is further enhanced by incorporating global and local reactivity descriptors. Additionally, an exploration of frontier molecular orbitals offers valuable insights into the molecule’s charge transfer characteristics. Moreover, a combined examination of internal and external molecular interactions unveils hyperconjugative interactions arising from charge delocalization, as elucidated through natural bond orbital (NBO) analysis.展开更多
Yttrium(Ⅲ)oxide or so-called diyttrium trioxide(Y_2O_3)is an excellent candidate ceramic material for optoelectronic applications.Structural,electrical conductivity,and dielectric relaxation properties of bulk yttri...Yttrium(Ⅲ)oxide or so-called diyttrium trioxide(Y_2O_3)is an excellent candidate ceramic material for optoelectronic applications.Structural,electrical conductivity,and dielectric relaxation properties of bulk yttrium(Ⅲ)oxide were studied.X-ray diffraction(XRD)results indicate that the yttrium(Ⅲ)oxide compound has a crystalline cubic phase.Fourier transform infrared(FTIR)technique was used to ascertain the chemical structure of the yttrium(Ⅲ)oxide compound.Impedance spectroscopy was used to analyze frequency-dependent electrical properties as a function of temperature in the range of 303-423 K and frequency range of 0.1 Hz-2 MHz.Impedance spectroscopy parameters such as dielectric constant,dielectric loss,loss factor,electric modulus,and complex impedance of the yttrium(Ⅲ)oxide compound were studied.The Nyquist plot describes the complex impedance of the yttrium(Ⅲ)oxide for different temperatures.The universal Jonscher's power law was used for the analysis of the complex electrical conductivity of the yttrium(Ⅲ)oxide compound.It is found that the real(σ')and imaginary(σ")parts of the complex conductivity increase with increasing frequency.The exponent frequency(s)equals unity,which confirms that the predominant conduction mechanism is a nearly constant loss(NCL)mechanism.DFT/TD-DFT studies using B3LYP/LanL2DZ level of theory were used to provide comparable theoretical data and electronic energy gap of HOMO→LUMO.展开更多
The corrosion rates of additive-manufactured Mg alloys are higher than their as-cast counterparts,possibly due to increased kinetics for the hydrogen evolution reaction on secondary phases,which may include oxide incl...The corrosion rates of additive-manufactured Mg alloys are higher than their as-cast counterparts,possibly due to increased kinetics for the hydrogen evolution reaction on secondary phases,which may include oxide inclusions.Scanning Kelvin Probe Force Microscopy demonstrated that MgO inclusions could act as cathodes for Mg corrosion,but their low conductivity likely precludes this.However,the density of state calculations through density functional theory using hybrid HSE06 functional revealed overlapping electronic states at the Mg/MgO interface,which facilitates electron transfers and participates in redox reactions.Subsequent determination of the hydrogen absorption energy at the Mg/MgO interface reveals it to be an excellent catalytic site,with HER being found to be a factor of 23x more efficient at the interface than on metallic Mg.The results not only support the plausibility of the Mg/MgO interface being an effective cathode to the adjacent anodic Mg matrix during corrosion but also contribute to the understanding of the enhanced cathodic activities observed during the anodic dissolution of magnesium.展开更多
Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects ...Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects of catalystscreening and exploring reaction conditions, with few accurate descriptions of the reaction kinetics and determination ofthe reaction mechanism. Here, we combined kinetics experiments and theoretical calculations to elucidate the kinetics andmechanism of acrylic acid hydration on a resin catalyst. The pseudo-homogeneous model, and Langmuir-Hinshelwood-Haugen-Watson and Elie-Riedel (ER) heterogeneous models were used to explain the experimental kinetics data. TheER model can explain the experimental data very well, suggesting strong adsorption of acrylic acid on the surface of theresin catalyst. Furthermore, density functional theory calculations show that the hydration follows a stepwise, rather than aconcerted, reaction pathway. The present study provides theoretical insights into the reaction mechanism and kinetics, fillingthe gap in our understanding of the reaction on a fundamental level.展开更多
Structural, electronic and optical properties of Sc-based aluminum-nitride alloy have been carried out with first-principles methods using both local density approximation (LDA) and Heyd-Scuseria-Ernzerhof (HSE) hybri...Structural, electronic and optical properties of Sc-based aluminum-nitride alloy have been carried out with first-principles methods using both local density approximation (LDA) and Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. This latter provides a more accurate description of the lattice parameters, enthalpy of formation, electronic and optical properties of our alloy than standard DFT. We found the transition from wurtzite to rocksalt structures at 61% of Sc concentration. By increasing the scandium concentration, the lattice parameters and the band gap decrease. The HSE band gap is in good agreement with available experimental data. The existence of the strong hybridization between Sc 3d and N 2p indicates the transport of electrons from Sc to N atoms. Besides, it is shown that the insertion of the Sc atom leads to the redshift of the optical absorption edge. The optical absorption of Sc<sub>x</sub>Al<sub>1-x</sub>N is found to decrease with increasing Sc concentrations in the low energy range. Because of this, Sc<sub>x</sub>Al<sub>1-x</sub>N have a great potential for applications in photovoltaics and photocatalysis.展开更多
基金Supported by the Natural Science Foundation of Shandong Province(No.Y2006B43)
文摘The spin crossover（SCO） compound [Fe（bapbpy）（NCS）2],where bapbpy contains two fused N,N-bis（2-pyridyl）amines,has been studied by DFT/TD-DFT/BS-DFT methods.Several density functionals and basis sets were used in the calculation to obtain optimized geometries of the compound in the low-（LS） and high-spin（HS） states.The vibrational modes and IR spectra,spin splitting energies,excited states and UV/Vis absorption spectra were obtained.The structural parameters of the calculated isolated complex are in good agreement with the X-ray data.We investigate three dimers of [Fe（bapbpy）（NCS）2] complex for their magnetic properties.It has been found that the complex（1,3） has ferromagnetic character while the others are antiferromagnetic in nature by using a broken symmetry approach in the DFT framework（BS-DFT） with support from the coupling constant values（J） and spin density plots.
文摘Based on density functional theory(DFT) and time-dependent density functional theory(TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer(ESIPT) process and photophysical properties of 2-(2’-hydroxyphenyl)-4-chloromethylthiazole(HCT) are studied. The electron-donating group(CH_(3), OH) and electronwithdrawing group(CF_(3), CHO) are introduced to analyze the changes of intramolecular H-bond, the frontier molecular orbitals, the absorption/fluorescence spectra, and the energy barrier of ESIPT process. The calculation results indicate that electron-donating group strengthens the intramolecular H-bond in the S_(1) state, and leads to an easier ESIPT process. The electron-withdrawing group weakens the corresponding H-bond and makes ESIPT process a little harder. Different substituents also affect the photophysical properties of HCT. The electron-withdrawing group(CF_(3), CHO) has a little effect on electronic spectra. The electron-donating group(CH_(3), OH) red-shifts both the absorption and fluorescence emission peaks of HCT, respectively, which causes the Stokes shift to increase.
文摘A charge transfer hydrogen bonded complex between the electron donor (proton acceptor) 2-amino-4,6-dimethylpyridine with the electron acceptor (proton donor) chloranilic acid has been synthesized and studied experimentally and theoretically. The stability constant recorded high values indicating the high stability of the formed complex. In chloroform, ethanol, methanol and acetonitrile were found the stoichiometric ratio 1:1. The solid complex was prepared and characterized by different spectroscopy techniques. FTIR, 1H and 13C NMR studies supported the presence of proton and charge transfers in the formed complex. Complemented with experimental results, molecular modelling using the density functional theory (DFT) calculations was carried out in the gas, chloroform and methanol phases where the existence of charge and hydrogen transfers. Finally, a good consistency between experimental and theoretical calculations was found confirming that the applied basis set is the suitable one for the system under investigation.
文摘Benzothiazole (BTH) and its derivatives are organic molecules with biologic actions. Because of their many applications, they are produced on a massive scale and used in a number of environmental compartments. Their discharge into water produces environmental problems, exposing our environment to public health problems. A solution that can contribute to their deterioration is becoming a necessity. For this reason, a conceptual analysis of the reactivity of benzothiazole and four of its compounds was undertaken in order to investigate certain aspects of their biodegradability. A theoretical investigations of the compounds studied were conducted in the gas and water phases with the most widely used density functional theory method, Becke-3-Parameter-Lee-Yang-Parr (B3LYP) with 6-31G+ (d, p) basis. Reactivity study calculated global indices of reactivity revealed that 2-SCH3_BTH is the most reactive. Dipole moment values analysis reveals that 2-NH2_BTH is the most soluble in water, while the lipophilicity shows that 2-NH2_BTH is the most hydrophilic compound. Thermodynamic parameters values reflect that reactions are respectively exothermic and spontaneous. By analyzing an Electrostatic Molecular Potential (EMP) map, researchers can pinpoint reactive sites on a molecule and anticipate its reactivity. This assessment is further enhanced by incorporating global and local reactivity descriptors. Additionally, an exploration of frontier molecular orbitals offers valuable insights into the molecule’s charge transfer characteristics. Moreover, a combined examination of internal and external molecular interactions unveils hyperconjugative interactions arising from charge delocalization, as elucidated through natural bond orbital (NBO) analysis.
基金supported by Taif University Researchers,Taif University,Taif,Saudi Arabia(grant numbers TURSP-2020/22)。
文摘Yttrium(Ⅲ)oxide or so-called diyttrium trioxide(Y_2O_3)is an excellent candidate ceramic material for optoelectronic applications.Structural,electrical conductivity,and dielectric relaxation properties of bulk yttrium(Ⅲ)oxide were studied.X-ray diffraction(XRD)results indicate that the yttrium(Ⅲ)oxide compound has a crystalline cubic phase.Fourier transform infrared(FTIR)technique was used to ascertain the chemical structure of the yttrium(Ⅲ)oxide compound.Impedance spectroscopy was used to analyze frequency-dependent electrical properties as a function of temperature in the range of 303-423 K and frequency range of 0.1 Hz-2 MHz.Impedance spectroscopy parameters such as dielectric constant,dielectric loss,loss factor,electric modulus,and complex impedance of the yttrium(Ⅲ)oxide compound were studied.The Nyquist plot describes the complex impedance of the yttrium(Ⅲ)oxide for different temperatures.The universal Jonscher's power law was used for the analysis of the complex electrical conductivity of the yttrium(Ⅲ)oxide compound.It is found that the real(σ')and imaginary(σ")parts of the complex conductivity increase with increasing frequency.The exponent frequency(s)equals unity,which confirms that the predominant conduction mechanism is a nearly constant loss(NCL)mechanism.DFT/TD-DFT studies using B3LYP/LanL2DZ level of theory were used to provide comparable theoretical data and electronic energy gap of HOMO→LUMO.
基金Agency for Science,Technology and Research(A*STAR),under the RIE2020 Advanced Manufacturing and Engineering(AME)Programmatic Grant(Grant no.A18B1b0061)。
文摘The corrosion rates of additive-manufactured Mg alloys are higher than their as-cast counterparts,possibly due to increased kinetics for the hydrogen evolution reaction on secondary phases,which may include oxide inclusions.Scanning Kelvin Probe Force Microscopy demonstrated that MgO inclusions could act as cathodes for Mg corrosion,but their low conductivity likely precludes this.However,the density of state calculations through density functional theory using hybrid HSE06 functional revealed overlapping electronic states at the Mg/MgO interface,which facilitates electron transfers and participates in redox reactions.Subsequent determination of the hydrogen absorption energy at the Mg/MgO interface reveals it to be an excellent catalytic site,with HER being found to be a factor of 23x more efficient at the interface than on metallic Mg.The results not only support the plausibility of the Mg/MgO interface being an effective cathode to the adjacent anodic Mg matrix during corrosion but also contribute to the understanding of the enhanced cathodic activities observed during the anodic dissolution of magnesium.
文摘Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects of catalystscreening and exploring reaction conditions, with few accurate descriptions of the reaction kinetics and determination ofthe reaction mechanism. Here, we combined kinetics experiments and theoretical calculations to elucidate the kinetics andmechanism of acrylic acid hydration on a resin catalyst. The pseudo-homogeneous model, and Langmuir-Hinshelwood-Haugen-Watson and Elie-Riedel (ER) heterogeneous models were used to explain the experimental kinetics data. TheER model can explain the experimental data very well, suggesting strong adsorption of acrylic acid on the surface of theresin catalyst. Furthermore, density functional theory calculations show that the hydration follows a stepwise, rather than aconcerted, reaction pathway. The present study provides theoretical insights into the reaction mechanism and kinetics, fillingthe gap in our understanding of the reaction on a fundamental level.
文摘Structural, electronic and optical properties of Sc-based aluminum-nitride alloy have been carried out with first-principles methods using both local density approximation (LDA) and Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. This latter provides a more accurate description of the lattice parameters, enthalpy of formation, electronic and optical properties of our alloy than standard DFT. We found the transition from wurtzite to rocksalt structures at 61% of Sc concentration. By increasing the scandium concentration, the lattice parameters and the band gap decrease. The HSE band gap is in good agreement with available experimental data. The existence of the strong hybridization between Sc 3d and N 2p indicates the transport of electrons from Sc to N atoms. Besides, it is shown that the insertion of the Sc atom leads to the redshift of the optical absorption edge. The optical absorption of Sc<sub>x</sub>Al<sub>1-x</sub>N is found to decrease with increasing Sc concentrations in the low energy range. Because of this, Sc<sub>x</sub>Al<sub>1-x</sub>N have a great potential for applications in photovoltaics and photocatalysis.
