Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe...Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.展开更多
Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a ...Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a temperature between 1100℃and 1200℃.The structure ofα-MoP_(2) and its relationship to other transition metal diphosphides are discussed.Surprisingly,the ambient pressure phase orthorhombicβ-MoP_(2)(space group Cmc21)is denser in structure thanα-MoP_(2).Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition fromβ-MoP_(2) to α-MoP_(2),suggesting thatα-MoP_(2) is a stable phase at ambient conditions;this is also supported by the total energy and phonon calculations.展开更多
The electronic structures and optical properties of the monoclinic ZrO2 (m-ZrO2) are investigated by means of first-principles local density approximation (LDA) + U approach.Without on-site Coulomb interactions,the ba...The electronic structures and optical properties of the monoclinic ZrO2 (m-ZrO2) are investigated by means of first-principles local density approximation (LDA) + U approach.Without on-site Coulomb interactions,the band gap of m-ZrO2 is 3.60 eV,much lower than the experimental value (5.8 eV).By introducing the Coulomb interactions of 4d orbitals on Zr atom (Ud) and of 2p orbitals on O atom (Up),we can reproduce the experimental value of the band gap.The calculated dielectric function of m-ZrO2 exhibits a small shoulder at the edge of the band gap in its imaginary part,while in the tetragonal ZrO2 and cubic ZrO2 it is absent,which is consistent with the experimental observations.The origin of the shoulder is attributed to the difference of electronic structures near the edge of the valence and conduction bands.展开更多
Nickel molybdate(NiMoO4)nanoparticles(NPs)were synthesized by sol-gel method.Utilizing water as solvent providescrystalline nanostructures.These nanocrystals were structurally characterized by X-ray diffraction,energy...Nickel molybdate(NiMoO4)nanoparticles(NPs)were synthesized by sol-gel method.Utilizing water as solvent providescrystalline nanostructures.These nanocrystals were structurally characterized by X-ray diffraction,energy dispersive X-ray analysis(EDX),and Fourier transform infrared spectra.Compositional stoichiometry was confirmed by EDX technique.The size and shapewere observed by scanning electron microscopy(SEM)and transmission electron microscope(TEM).It was found that the obtainedNPs were pure and single phase crystalline with monoclinic structure.The optical properties were studied by ultraviolet-visiblediffuse reflectance spectroscopy(UV-Vis-DRS)and photoluminescence(PL)measurements at room temperature.The magneticproperties were studied by vibrating sample magnetometer(VSM)and results showed superparamagnetic behavior of the obtainednanoparticles.Photocatalytic activity of NiMoO4was studied.The photocatalytic activity of NiMoO4was enhanced with the additionof TiO2.The catalysts NiMoO4,TiO2and NiMoO4-TiO2nanocomposites(NC)were tested for photocatalytic degradation(PCD)of4-chlorophenol(4-CP).It was found that PCD efficiency of NiMoO4-TiO2NC was higher than that of pure NiMoO4and TiO2.展开更多
The crystal structure of trichosanthin (TCS) in space group C2 hasbeen refined by PROLSQ and XPLOR to an R-factor of 0. 204 for 33, 531 reflectionswith F。≥2-σ(F。) between 6 to 1. 9 A resolution. The root mean squa...The crystal structure of trichosanthin (TCS) in space group C2 hasbeen refined by PROLSQ and XPLOR to an R-factor of 0. 204 for 33, 531 reflectionswith F。≥2-σ(F。) between 6 to 1. 9 A resolution. The root mean square(r. m. s. ) devi-ations of bond lengths and bond angles from the standard values are 0. 015 A and 2.77°, respectively. The overall fold of the molecule of TCS is, in general, similar to oth-er RIPs, but there are some differences in secondary structure and in the active sitecleft. An overlay of the two molecules (shown by Mol. A and Mol. B), which are notrelated by symmetry in an asymmetric unit, results in an r. m. s. deviation of 0. 850Afor the main chain atoms. The backbones of the C-terminus of the two molecules arequite different. The structures of the water in two molecules are not completely analo-gous. In the active site cleft of Mol. B, the bonding sites of three water molecules toprotein are similar to those of N atoms of formycin ring in the structure of pokeweedantiviral protein complexed with formycin 5-monophosphate, and the side chains of twoTyr70 in the two crystalline forms of TCS show a similar orientation, which is differentfrom that of the corresponding residue in ricin A-chain.展开更多
The structural relaxation, electronic structures, formation energies and transition energy levels of monoclinic HfO2 with neutral and charged oxygen vacancies have been studied using the first principles calculation b...The structural relaxation, electronic structures, formation energies and transition energy levels of monoclinic HfO2 with neutral and charged oxygen vacancies have been studied using the first principles calculation based on density-functional theory and generalized gradient approximation. The results show that oxygen vacancies with different charge states can be formed in m-HfO2 under both oxygen-rich and oxygen-poor conditions. Especially, lower formation energy is obtained in poor oxygen environment. In the presence of oxygen vacancies with different charge states, extra levels can be observed at different positions in the band gap. And the most stable charge states are obtained for varying Fermi levels in the HfO2 band gap. It is found that oxygen vacancy in m-HfO2 has a negative-U behavior.展开更多
基金Project supported by the Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,China
文摘Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.92065201,11874264,and 11974154)the Starting Grant of ShanghaiTech University and Analytical Instrumentation Center,SPST,ShanghaiTech University (Grant No.SPST-AIC10112914)support from the Natural Science Foundation of Shandong Province,China (Grant No.ZR2022MA004)。
文摘Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a temperature between 1100℃and 1200℃.The structure ofα-MoP_(2) and its relationship to other transition metal diphosphides are discussed.Surprisingly,the ambient pressure phase orthorhombicβ-MoP_(2)(space group Cmc21)is denser in structure thanα-MoP_(2).Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition fromβ-MoP_(2) to α-MoP_(2),suggesting thatα-MoP_(2) is a stable phase at ambient conditions;this is also supported by the total energy and phonon calculations.
基金the National Natural Science Foundation of China，the Strategic Programs for Innovative Research，the Computational Materials Science Initiative，the Yukawa International Program for Quark-Hadron Sciences at YITP,Kyoto University
文摘The electronic structures and optical properties of the monoclinic ZrO2 (m-ZrO2) are investigated by means of first-principles local density approximation (LDA) + U approach.Without on-site Coulomb interactions,the band gap of m-ZrO2 is 3.60 eV,much lower than the experimental value (5.8 eV).By introducing the Coulomb interactions of 4d orbitals on Zr atom (Ud) and of 2p orbitals on O atom (Up),we can reproduce the experimental value of the band gap.The calculated dielectric function of m-ZrO2 exhibits a small shoulder at the edge of the band gap in its imaginary part,while in the tetragonal ZrO2 and cubic ZrO2 it is absent,which is consistent with the experimental observations.The origin of the shoulder is attributed to the difference of electronic structures near the edge of the valence and conduction bands.
基金support from the Caplin Point Laboratories Limited,Chennai,India
文摘Nickel molybdate(NiMoO4)nanoparticles(NPs)were synthesized by sol-gel method.Utilizing water as solvent providescrystalline nanostructures.These nanocrystals were structurally characterized by X-ray diffraction,energy dispersive X-ray analysis(EDX),and Fourier transform infrared spectra.Compositional stoichiometry was confirmed by EDX technique.The size and shapewere observed by scanning electron microscopy(SEM)and transmission electron microscope(TEM).It was found that the obtainedNPs were pure and single phase crystalline with monoclinic structure.The optical properties were studied by ultraviolet-visiblediffuse reflectance spectroscopy(UV-Vis-DRS)and photoluminescence(PL)measurements at room temperature.The magneticproperties were studied by vibrating sample magnetometer(VSM)and results showed superparamagnetic behavior of the obtainednanoparticles.Photocatalytic activity of NiMoO4was studied.The photocatalytic activity of NiMoO4was enhanced with the additionof TiO2.The catalysts NiMoO4,TiO2and NiMoO4-TiO2nanocomposites(NC)were tested for photocatalytic degradation(PCD)of4-chlorophenol(4-CP).It was found that PCD efficiency of NiMoO4-TiO2NC was higher than that of pure NiMoO4and TiO2.
文摘The crystal structure of trichosanthin (TCS) in space group C2 hasbeen refined by PROLSQ and XPLOR to an R-factor of 0. 204 for 33, 531 reflectionswith F。≥2-σ(F。) between 6 to 1. 9 A resolution. The root mean square(r. m. s. ) devi-ations of bond lengths and bond angles from the standard values are 0. 015 A and 2.77°, respectively. The overall fold of the molecule of TCS is, in general, similar to oth-er RIPs, but there are some differences in secondary structure and in the active sitecleft. An overlay of the two molecules (shown by Mol. A and Mol. B), which are notrelated by symmetry in an asymmetric unit, results in an r. m. s. deviation of 0. 850Afor the main chain atoms. The backbones of the C-terminus of the two molecules arequite different. The structures of the water in two molecules are not completely analo-gous. In the active site cleft of Mol. B, the bonding sites of three water molecules toprotein are similar to those of N atoms of formycin ring in the structure of pokeweedantiviral protein complexed with formycin 5-monophosphate, and the side chains of twoTyr70 in the two crystalline forms of TCS show a similar orientation, which is differentfrom that of the corresponding residue in ricin A-chain.
基金supported by the National Natural Science Foundation of China (No.51202196)the Northwestern Polytechnical University (NPU) Foundation for Fundamental Research (No.JC201111)+1 种基金the Research Fund of the State Key Laboratory of Solidification Processing (NWPU,(No.58-TZ-2011)the 111 Project (No.B08040)
文摘The structural relaxation, electronic structures, formation energies and transition energy levels of monoclinic HfO2 with neutral and charged oxygen vacancies have been studied using the first principles calculation based on density-functional theory and generalized gradient approximation. The results show that oxygen vacancies with different charge states can be formed in m-HfO2 under both oxygen-rich and oxygen-poor conditions. Especially, lower formation energy is obtained in poor oxygen environment. In the presence of oxygen vacancies with different charge states, extra levels can be observed at different positions in the band gap. And the most stable charge states are obtained for varying Fermi levels in the HfO2 band gap. It is found that oxygen vacancy in m-HfO2 has a negative-U behavior.
