The energy bands, electronic structures and relationship between structures and properties of the crystalline alkali metal azides, LiN3, α-NaN3 and KN3, are investigated at the DFT-B3LYP level. The crystalline bulks ...The energy bands, electronic structures and relationship between structures and properties of the crystalline alkali metal azides, LiN3, α-NaN3 and KN3, are investigated at the DFT-B3LYP level. The crystalline bulks are predicted to be insulator, speculated from their band gaps of ca. 0.23-0.25 a.u. and from their level frontier bands. The atomic overlaps and electron densities show that the metals and the azides are combined by ionic bonds. The crystal lattice energies, being corrected for the basis set superposition errors, are -852.30, -771.45 and - 614.78 kJ·mol-1 for LiN3, a-NaN3 and KN3 respectively. These values are similar to those by Gray’s approximate method. The frontier crystal orbital mainly consists of the atomic orbital of the terminal nitrogen of azides. The contribution of the metallic orbital to the LUMO is very small. The electron transition from the HOMO to the LUMO is difficult to occur. Hence all the alkali metal azides are expected to be insensitive explosives, according to the '展开更多
Molecular dynamics （MD） simulation was performed to study ethene adsorption, polarization and diffusion in orthorhombic and monoclinic MFI and H[Al] ZSM-5 at 300 K. The resuits show that the interaction between ethe...Molecular dynamics （MD） simulation was performed to study ethene adsorption, polarization and diffusion in orthorhombic and monoclinic MFI and H[Al] ZSM-5 at 300 K. The resuits show that the interaction between ethene molecule and orthorhombic MFI is the strongest.Ethene molecules possess relatively low energy in the lattice of orthorhombic MFI. The existence of Al and Brnsted H atoms in the framework of H[AI]ZSM-5 can lower the energy of adsorbed ethene molecules. At the edges of intersections of channels, especially those near Al sites,ethene molecules are polarized most. Ethene molecules prefer the locations at the centers of channel intersections. The diffusion coefficients of ethene in the lattices of orthorhombic, monoclinic MFI and H[AI]ZSM-5 are 2.7 x 10<sup>-9</sup>, 2.1 x l0<sup>-9</sup>, 1.6 x 10<sup>-9</sup> m<sup>2</sup>·s<sup>-1</sup>, respectively. The infrared spectrum of ethene in the framework of H[Al] ZSM-5 shows five vibration peaks (v<sub>10</sub>,v<sub>7</sub>, v<sub>12</sub>, v<sub>11</sub> and V<sub>9</sub>), which is consistent with the experimental result.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No. 20173028)the Postdoctoral Foundation of Chinese Ministry of Education.
文摘The energy bands, electronic structures and relationship between structures and properties of the crystalline alkali metal azides, LiN3, α-NaN3 and KN3, are investigated at the DFT-B3LYP level. The crystalline bulks are predicted to be insulator, speculated from their band gaps of ca. 0.23-0.25 a.u. and from their level frontier bands. The atomic overlaps and electron densities show that the metals and the azides are combined by ionic bonds. The crystal lattice energies, being corrected for the basis set superposition errors, are -852.30, -771.45 and - 614.78 kJ·mol-1 for LiN3, a-NaN3 and KN3 respectively. These values are similar to those by Gray’s approximate method. The frontier crystal orbital mainly consists of the atomic orbital of the terminal nitrogen of azides. The contribution of the metallic orbital to the LUMO is very small. The electron transition from the HOMO to the LUMO is difficult to occur. Hence all the alkali metal azides are expected to be insensitive explosives, according to the '
文摘Molecular dynamics （MD） simulation was performed to study ethene adsorption, polarization and diffusion in orthorhombic and monoclinic MFI and H[Al] ZSM-5 at 300 K. The resuits show that the interaction between ethene molecule and orthorhombic MFI is the strongest.Ethene molecules possess relatively low energy in the lattice of orthorhombic MFI. The existence of Al and Brnsted H atoms in the framework of H[AI]ZSM-5 can lower the energy of adsorbed ethene molecules. At the edges of intersections of channels, especially those near Al sites,ethene molecules are polarized most. Ethene molecules prefer the locations at the centers of channel intersections. The diffusion coefficients of ethene in the lattices of orthorhombic, monoclinic MFI and H[AI]ZSM-5 are 2.7 x 10<sup>-9</sup>, 2.1 x l0<sup>-9</sup>, 1.6 x 10<sup>-9</sup> m<sup>2</sup>·s<sup>-1</sup>, respectively. The infrared spectrum of ethene in the framework of H[Al] ZSM-5 shows five vibration peaks (v<sub>10</sub>,v<sub>7</sub>, v<sub>12</sub>, v<sub>11</sub> and V<sub>9</sub>), which is consistent with the experimental result.
