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991.
The B3LYP/6-31G (d) method of density functional theory (DFT) was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. The heat of formation (HOF) and calculated density were estimated to evaluate the detonation properties using Kamlet–Jacobs equations. Thermal stability of 3,5,7,10,12,14,15,16-octanitro- 3,5,7,10,12,14,15,16-octaaza-heptacyclo[7.5.1.12,8.01,11.02,6.04,13.06,11]hexadecane (cage-tetranitrotetraazabicyclooctane) was investigated by calculating the bond dissociation energy (BDE) at unrestricted B3LYP/6-31G (d) level. The calculated results show that the N–NO2 bond is a trigger bond during thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to Pna21 space group, with cell parameters a?=?12.840 Å, b?=?9.129 Å, c?=?14.346 Å, Z?=?6 and ρ?=?2.292 g·cm?3. Both the detonation velocity of 9.96 km·s?1 and the detonation pressure of 47.47 GPa are better than those of CL-20. According to the quantitative standard of energetics and stability, as a high energy density compound (HEDC), cage-tetranitrotetraazabicyclooctane essentially satisfies this requirement. 相似文献
992.
Xiao Ran Zhao Yu Jie Wu Juan Han Qian Jin Shen Wei Jun Jin 《Journal of molecular modeling》2013,19(1):299-304
MP2(full)/aug-cc-pVDZ(-PP) computations predict that new triangular bonding complexes (where X? is a halide and H–C refers to a protic solvent molecule) consist of one halogen bond and two hydrogen bonds in the gas phase. Carbon tetrabromide acts as the donor in the halogen bond, while it acts as an acceptor in the hydrogen bond. The halide (which commonly acts as an acceptor) can interact with both carbon tetrabromide and solvent molecule (CH3CN, CH2Cl2, CHCl3) to form a halogen bond and a hydrogen bond, respectively. The strength of the halogen bond obeys the order CBr4???Cl? > CBr4???Br? > CBr4???I?. For the hydrogen bonds formed between various halides and the same solvent molecule, the strength of the hydrogen bond obeys the order C-H???Cl? > C-H???Br? > C-H???I?. For the hydrogen bonds formed between the same halide and various solvent molecules, the interaction strength is proportional to the acidity of the hydrogen in the solvent molecule. The diminutive effect is present between the hydrogen bonds and the halogen bond in chlorine and bromine triangular bonding complexes. Complexes containing iodide ion show weak cooperative effects. Figure
The triangular bonding complexes consisting of halogen bond and hydrogen bonds were predict in the gas phase by computational quantum chemistry. 相似文献
993.
The interaction between M (M?=?Ca, Yb) atom and C74 (D 3h) has been investigated by all electron relativistic density function theory. With the aid of the representative patch of C74 (D 3h), we studied the interaction between C74 (D 3h) and M (M?=?Ca, Yb) atom and obtained the interaction potential. Optimized structures show that there are three equivalent stable isomers and there is one transition state between every two stable isomers. According to the minimum energy pathway, the possible movement trajectory of M (M?=?Ca, Yb) atom in the C74 (D 3h) cage is explored. The calculated energy barrier for Yb atoms moving from the stable isomer to the transition state is 10.4 kcal mol?1 and the energy barrier for Ca atoms is 6.1 kcal mol?1. The calculated NMR spectra of M@C74 (M?=?Ca, Yb) are in good agreement with the experimental data. There are nine lines in the spectra: one 1/6 intensity signal, four half intensity signals and four full intensity signals. 相似文献
994.
Wenkai Tian Xin Huang Qingzhong Li Wenzuo Li Jianbo Cheng Baoan Gong 《Journal of molecular modeling》2013,19(3):1311-1318
Quantum chemical calculations have been performed for the complexes Li3OCCX–Y (X?=?Cl, Br, H; Y?=?NH3, H2O, H2S) and Li3OCN–X′Y′ (X′Y′?=?ClF, BrCl, BrF, HF) to study the role of superalkalis in hydrogen and halogen bonds. The results show that the presence of an Li3O cluster in a Lewis acid weakens its acidity, while its presence in a Lewis base enhances its basicity. Furthermore, the latter effect is more prominent than the former one, and the presence of an Na3O cluster causes an even greater effect than Li3O. The strengths of hydrogen and halogen bonds were analyzed using molecular electrostatic potentials. The contributions of superalkalis to the strength of hydrogen and halogen bonds were elucidated by analyzing differences in electron density. 相似文献
995.
Xiaohua Liu Tiejun Zhu Heng Wang Lipeng Hu Hanhui Xie Guangyu Jiang G. Jeffrey Snyder Xinbing Zhao 《Liver Transplantation》2013,3(9):1238-1244
Understanding the electron and phonon transport characteristics is crucial for designing and developing high performance thermoelectric materials. Weak scattering effects on charge carriers, characterized by deformation potential and alloy scattering potential, are favorable for thermoelectric solid solutions to enable high carrier mobility and thereby promising thermoelectric performance. Mg2(Si,Sn) solid solutions have attracted much attention due to their low cost and environmental compatibility. Usually, their high thermoelectric performance with ZT ~ 1 is ascribed to the band convergence and reduced lattice thermal conductivity caused by alloying. In this work, both a low deformation potential Ξ = 13 eV and a low alloy scattering potential U = 0.7 eV are found for the thermoelectric alloys by characterizing and modeling of thermoelectric transport properties. The band convergence is also verified by the increased density‐of‐states effective mass. It is proposed that, in addition to band convergence and reduced lattice thermal conductivity, the low deformation potential and alloy scattering potential are additional intrinsic features that contribute to the high thermoelectric performance of the solid solutions. 相似文献
996.
997.
998.
Changhun Park Mingshou Lu Seokhun Yun Kyungmoon Park Jinwon Lee 《Bioprocess and biosystems engineering》2013,36(6):845-855
The efficiency of the bioconversion process and the achievable end-product concentration decides the economic feasibility of microbial 2,3-butanediol (2,3-BDO) production. In 2,3-BDO production, optimization of culture condition is required for cell growth and metabolism. Also, the pH is an important factor that influences microbial performance. For different microorganisms and substrates, it has been shown that the distribution of the metabolites in 2,3-BDO fermentation is greatly affected by pH, and the optimum pH for 2,3-BDO production seems dependently linked to the particular strain and the substrate employed. Quantification analysis of intracellular metabolites and metabolic flux analysis (MFA) were used to investigate the effect of pH on the Klebsiella oxytoca producing 2,3-BDO and other organic acids. The main objectives of MFA are the estimation of intracellular metabolic fluxes and the identification of rate-limiting step and the key enzymes. This study was conducted under continuous aerobic conditions at different dilution rates (0.1, 0.2, and 0.3 h?1) and different pH values (pH 5.5 and 7.0) for the steady-state experimental data. In order to obtain the flux distribution, the extracellular specific rates were calculated from the experimental data using the metabolic network model of K. oxytoca. Intracellular metabolite concentration profiles were generated using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. 相似文献
999.
Seok-In Yun Seong-Joo Gang Hee-Myong Ro Min-Jin Lee Woo-Jung Choi Seong-Gu Hong Kwon-Kyoo Kang 《Bioprocess and biosystems engineering》2013,36(5):591-595
Conversion of synthesis gas (CO and H2) to ethanol can be an alternative, promising technology to produce biofuels from renewable biomass. To distinguish microbial utilization of carbon source between fructose and synthesis gas CO and to evaluate biological production of ethanol from CO, we adopted the 13C-enrichment of the CO substrate and hypothesized that the residual increase in δ13C of the cell biomass would reflect the increased contribution of 13C-enriched CO. Addition of synthesis gas to live culture medium for ethanol fermentation by Clostridum ljungdahlii increased the microbial growth and ethanol production. Despite the high 13C-enrichment in CO (99 atom % 13C), however, microbial δ13C increased relatively small compared to the microbial growth. The uptake efficiency of CO estimated using the isotope mass balance equation was also very low: 0.0014 % for the low CO and 0.0016 % for the high CO treatment. Furthermore, the fast production of ethanol in the early stage indicated that the presence of sugar in fermentation medium would limit the utilization of CO as a carbon source by C. ljungdahlii. 相似文献
1000.