In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction w...In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction with the complex rotation of the Hamiltonian,were used to determine their wave functions.The electron densities,Fukui functions,and values of the hyper-radius<r^2>were computed from these wave functions.The Fukui functions have negative regions in the valence shell in addition to the inner shell regions,indicating screening effects of the outer temporary electron.Selected configuration interactions with up to quadruple excitations were used along the trajectories and for computing the final wave function.Based on this data,the densities,Fukui functions,and<r^2>were calculated.展开更多
Multi-scale quantum-mechanical/molecular-mechanical(QM/MM) and large-scale QM simulation provide valuable insight into enzyme mechanism and structure-property relationships. Analysis of the electron density afforded t...Multi-scale quantum-mechanical/molecular-mechanical(QM/MM) and large-scale QM simulation provide valuable insight into enzyme mechanism and structure-property relationships. Analysis of the electron density afforded through these methods can enhance our understanding of how the enzyme environment modulates reactivity at the enzyme active site. From this perspective, tools from conceptual density functional theory to interrogate electron densities can provide added insight into enzyme function. We recently introduced the highly parallelizable Fukui shift analysis(FSA) method, which identifies how frontier states of an active site are altered by the presence of an additional QM residue to identify when QM treatment of a residue is essential as a result of quantum-mechanically affecting the behavior of the active site. We now demonstrate and analyze distance and residue dependence of Fukui function shifts in pairs of residues representing different non-covalent interactions. We also show how the interpretation of the Fukui function as a measure of relative nucleophilicity provides insight into enzymes that carry out S_N2 methyl transfer. The FSA method represents a promising approach for the systematic, unbiased determination of quantum mechanical effects in enzymes and for other complex systems that necessitate multi-scale modeling.展开更多
Triacetone triperoxide （TATP） is more sensitive than diacetone diperoxide （DADP） in the solid-state explosion. To explain this reactivity difference, we analyzed the electronic structures and properties of the cry...Triacetone triperoxide （TATP） is more sensitive than diacetone diperoxide （DADP） in the solid-state explosion. To explain this reactivity difference, we analyzed the electronic structures and properties of the crystals of both compounds by using Ab initio method to calculate the structures of their individual molecules as well as their lattice structures and particularly calculating Nuclear Fukui function to gain insight into the sensitivity of the initial, rate-determining step of their decomposition. Our results indicate that TATP and DADP crystal structures exhibit significantly different electronic proper- ties. Most notably, the electronic structure of the TATP crystal shows asymmetry among its reactive oxygen atoms as supported by magnitudes of their nuclear Fukui functions. The greater explosion sensitivity of crystalline TATP may be attributed to the properties of its electronic structure. The electronic calculations provided valuable insight into the decomposition sensitivity difference between TATP and DADP crystals.展开更多
合成了用于辐照接枝制备质子交换膜的对苯乙烯磺酰氯单体,并采用红外光谱(FTIR)、核磁共振氢谱(1 H NMR)和核磁共振碳谱(13 C NMR)对其结构进行了表征分析,分析结果表明:成功得到了目标产物对苯乙烯磺酰氯。基于密度泛函的量子化学方法...合成了用于辐照接枝制备质子交换膜的对苯乙烯磺酰氯单体,并采用红外光谱(FTIR)、核磁共振氢谱(1 H NMR)和核磁共振碳谱(13 C NMR)对其结构进行了表征分析,分析结果表明:成功得到了目标产物对苯乙烯磺酰氯。基于密度泛函的量子化学方法对合成的单体进行了理论模拟,结果表明该单体具有与苯乙烯一致的电荷分布,乙烯基α碳位易发生亲电反应,β碳位易发生亲核反应和自由基反应。采用辐射接枝聚合的方法,将对苯乙烯磺酰氯单体接枝到聚全氟乙丙烯薄膜基材上并通过后处理制备用于燃料电池的质子交换膜,结果表明膜的质子传导率与接枝率正相关,在20Gy·min^(-1)和40Gy·min^(-1)条件下膜的室温质子传导率分别为45.74mS·cm^(-1)和47.46mS·cm^(-1),20Gy·min^(-1)条件下制备的质子交换膜其传导率在75℃时可达84.56mS·cm^(-1)。展开更多
文摘In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction with the complex rotation of the Hamiltonian,were used to determine their wave functions.The electron densities,Fukui functions,and values of the hyper-radius<r^2>were computed from these wave functions.The Fukui functions have negative regions in the valence shell in addition to the inner shell regions,indicating screening effects of the outer temporary electron.Selected configuration interactions with up to quadruple excitations were used along the trajectories and for computing the final wave function.Based on this data,the densities,Fukui functions,and<r^2>were calculated.
文摘Multi-scale quantum-mechanical/molecular-mechanical(QM/MM) and large-scale QM simulation provide valuable insight into enzyme mechanism and structure-property relationships. Analysis of the electron density afforded through these methods can enhance our understanding of how the enzyme environment modulates reactivity at the enzyme active site. From this perspective, tools from conceptual density functional theory to interrogate electron densities can provide added insight into enzyme function. We recently introduced the highly parallelizable Fukui shift analysis(FSA) method, which identifies how frontier states of an active site are altered by the presence of an additional QM residue to identify when QM treatment of a residue is essential as a result of quantum-mechanically affecting the behavior of the active site. We now demonstrate and analyze distance and residue dependence of Fukui function shifts in pairs of residues representing different non-covalent interactions. We also show how the interpretation of the Fukui function as a measure of relative nucleophilicity provides insight into enzymes that carry out S_N2 methyl transfer. The FSA method represents a promising approach for the systematic, unbiased determination of quantum mechanical effects in enzymes and for other complex systems that necessitate multi-scale modeling.
基金This research was supported by NSF （DMR- 0449633）. PPZ thanks the financial support by the National Natural Science Foundation of China （Grant No. 21403097） and the Fundamental Research Funds for the Central Universities （lzujbky-2014-182）. The authors would like to thank Dr. Shaoxin Feng for his technical supports on this project. TL also thanks Dr. Shubin Liu （UNC） for sharing his insights on DFT.
文摘Triacetone triperoxide （TATP） is more sensitive than diacetone diperoxide （DADP） in the solid-state explosion. To explain this reactivity difference, we analyzed the electronic structures and properties of the crystals of both compounds by using Ab initio method to calculate the structures of their individual molecules as well as their lattice structures and particularly calculating Nuclear Fukui function to gain insight into the sensitivity of the initial, rate-determining step of their decomposition. Our results indicate that TATP and DADP crystal structures exhibit significantly different electronic proper- ties. Most notably, the electronic structure of the TATP crystal shows asymmetry among its reactive oxygen atoms as supported by magnitudes of their nuclear Fukui functions. The greater explosion sensitivity of crystalline TATP may be attributed to the properties of its electronic structure. The electronic calculations provided valuable insight into the decomposition sensitivity difference between TATP and DADP crystals.
基金supported by the National Natural Science Foundation of China(21483083,21133005)the Natural Science Foundation of Liaoning Province,China(2014020150)~~
文摘合成了用于辐照接枝制备质子交换膜的对苯乙烯磺酰氯单体,并采用红外光谱(FTIR)、核磁共振氢谱(1 H NMR)和核磁共振碳谱(13 C NMR)对其结构进行了表征分析,分析结果表明:成功得到了目标产物对苯乙烯磺酰氯。基于密度泛函的量子化学方法对合成的单体进行了理论模拟,结果表明该单体具有与苯乙烯一致的电荷分布,乙烯基α碳位易发生亲电反应,β碳位易发生亲核反应和自由基反应。采用辐射接枝聚合的方法,将对苯乙烯磺酰氯单体接枝到聚全氟乙丙烯薄膜基材上并通过后处理制备用于燃料电池的质子交换膜,结果表明膜的质子传导率与接枝率正相关,在20Gy·min^(-1)和40Gy·min^(-1)条件下膜的室温质子传导率分别为45.74mS·cm^(-1)和47.46mS·cm^(-1),20Gy·min^(-1)条件下制备的质子交换膜其传导率在75℃时可达84.56mS·cm^(-1)。
