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用密度泛函理论(DFT)研究了甲醇与一氧化碳的微观反应机理. 在B3LYP/6-311++G(d,p)水平上优化了反应物、过渡态及产物的几何构型, 并通过振动分析和内禀反应坐标方法(IRC)分别确认了过渡态的结构与反应途径. 在CCSD/6-311++G(d,p)水平上进行能量校正, 并根据计算的势能面探讨了CH3OH+CO反应机理. 结果表明, CH3OH+CO反应体系有三个可能的反应通道, 产物分别为甲酸甲酯、乙酸、羟基乙醛. 在无催化条件下, 计算得到生成甲酸甲酯、乙酸和羟基乙醛的反应活化能分别是364.715, 460.775和611.402 kJ•mol-1, 生成甲酸甲酯和羟基乙醛的反应为吸热反应, 而生成乙酸的反应为放热反应. 相似文献
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采用荧光猝灭法研究了两种辅酶,还原型烟酰胺嘌呤二核苷酸(NADH)、氧化型硫代烟酰胺腺嘌呤二核苷酸(Thio-NAD+)与3α-羟类固醇脱氢酶(3α-HSD)的相互作用。研究结果表明,NADH和Thio-NAD+的加入均能使3α-HSD的内源性荧光发生猝灭,其猝灭机制均属于生成复合物的静态猝灭;25℃下NADH、Thio-NAD+与3α-HSD的结合常数分别为7.38×104、1.23×104L.mol-1;37℃下NADH、Thio-NAD+与3α-HSD的结合常数分别为4.69×104、9.74×103L.mol-1;NADH与3α-HSD的结合作用力为氢键和范德华力,Thio-NAD+与3α-HSD的结合作用力主要为静电引力和疏水作用力;NADH和Thio-NAD+均能使3α-HSD构象发生变化,导致色氨酸残基所处环境极性增大。 相似文献
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Zero-field splitting parameters and local structures for tetragonal Cr2+ centers in Cr2+-doped ZnSe semiconductors 下载免费PDF全文
The inter-relation between zero-field splitting (ZFS) parameters and local lattice structures of the (CrSe4)6 clusters in ZnSe semiconductors has been established by using the complete diagonalization (of the energy matrix) method. On the basis of this, the local lattice distortions, the ZFS parameters D, a, F and the optical spectrum for Cr2+ ions doped into ZnSe are theoretically investigated, and the contributions of the spin singlets have been taken into account. The calculated ZFS parameters are in good agreement with the experimental values. From our calculations, the tetragonal distortion parameters AR = 0.091A and Aθ = 4.28° of Cr2+ in ZnSe are acquired, and the results suggest that there exists a tetragonal expansion distortion for the local lattice structure of (CrSe4)6- clusters in ZnSe crystals. The influence of the spin singlets on ZFS parameters is also discussed, indicating that the contributions to ZFS parameters a and F cannot be ignored. 相似文献
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WANG Yi-Hong WANG Sheng-Kui 《理论物理通讯》2008,50(8):299-302
In this paper, with the aid of symbolic computation, we present a uniform method for constructing soliton solutions and periodic solutions to (2+1)-dimensional Toda lattice equation. 相似文献
207.
Tunneling spectra of underdoped Bi_2Sr_2Ca_(1-x)Y_xCu_2O_(8+δ) intrinsic Josephson junctions 下载免费PDF全文
<正>Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi_2Sr_2Ca_(1-x)Y_xCu-2O_(8+δ) single crystals with a T_c of 80 K.Tunneling spectra at the temperatures ranging from 4.2 K to 295 K are measured.A pulse technique is used to reduce sample heating for the measurement near pseudogap opening temperature T~*~280 K.Our experimental results show that the superconducting gap,the peak-dip separation,and the pseudogap opening temperature are all increased as compared with those from near optimally doped samples,which requires further theoretical analysis in the future. 相似文献