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71.
72.
Yu. A. Borisov Yu. A. Zolotarev E. V. Laskatelev N. F. Myasoedov 《Russian Chemical Bulletin》1997,46(3):407-409
The simplest quantum-chemical models of hydrogen spillover over a graphite-like surface as a proton or radical have been considered.
The condensed planar C24H12 molecule was used as a model surface. Theab initio calculations of the interaction of hydrogen with the model surface were carried out by the restricted Hartree-Fock (HF) method
in the STO-3G and 6-31 G* basis sets. The radical hydrogen can not bind to such a surface, whereas the proton binds to it with an energy release of
186 kcal mol−1. The activation energy of the transfer of the proton between two neighboring carbon atoms (10 kcal mol−1) has been determined. The simplest model of the hydrogen migration as a proton over the model surface can be used for describing
the spillover of hydrogen over the graphite surface.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 428–430, March, 1997. 相似文献
73.
74.
在MP2水平上,用aug-cc-pVTZ基组对COC l2…NH3和COC l2…H2S体系进行几何优化和频率计算,同时使用Counterpoise技术进行BSSE校正,分别得到4个COC l2…NH3和2个COC l2…H2S无虚频的稳定结构:N(S)…C连接的构型(Ⅰ,Ⅱ,Ⅴ)和N(S)…C—lC直线型连接的构型(Ⅲ,Ⅳ,Ⅵ).第一类构型比第二类构型相互作用能更大、更稳定.在得到的6个稳定络合物中,络合物Ⅰ是最稳定的. 相似文献
75.
Several methodologies were employed to calculate the Gibbs standard free energy of binding for a collection of protein-ligand complexes, where the ligand is a peptide and the protein is representative for various protein families. Almost 40 protein-ligand complexes were employed for a continuum approach, which considers the protein and the peptide at the atomic level, but includes solvent as a polarizable continuum. Five protein-ligand complexes were employed for an all-atom approach that relies on a combination of the double decoupling method with thermodynamic integration and molecular dynamics. These affinities were also computed by means of the linear interaction energy method. Although it generally proved rather difficult to predict the absolute free energies correctly, for some protein families the experimental ranking order was correctly reproduced by the continuum and all-atom approach. Considerable attention has also been given to correctly analyze the affinities of charged peptides, where it is required to judge the effect of one or more ions that are being decoupled in an all-atom approach to preserve electroneutrality. The various methods are further judged upon their merits. 相似文献
76.
CCl2自由基与H2O分子反应动力学研究 总被引:2,自引:0,他引:2
用213 nm激光光解CCl4产生CCl2自由基,用LP LIF技术测定了室温下基态CCl2自由基与H2O分子的反应速率常数为(5.45±0.95)×10-14 cm3•molecule-1•s-1.在G2MP2理论水平上计算了CCl2+H2O反应的最低单重态势能面,揭示了插入与加成 消除两种反应机理,得到了三个可能的产物通道:HCl+HClCO、HCl+trans ClCOH以及HCl+cis ClCOH.并用RRKM TST和传统过渡态理论计算了这三个通道的分支比及其温度效应.结果说明在低温下(273 K),插入机理的产物通道的分支比远大于加成 消除机理的产物通道, HCl+HClCO是主要产物,分支比为77.4%,其次是HCl+cis ClCOH,分支比为22.6%.而在高温下(3000 K),加成 消除机理的反应通道大于插入机理, HCl+trans ClCOH分支比为82.3%. 相似文献
77.
Ionization and dissociation of nitrosyl chloride ClNO were studied using femtosecond laser mass spectra tech-nique.Strong fragmental ions NO~ and Cl~ were observed with the laser intensity varied from 3.2×10~(14) to 2.5×10~(15) W/cm~2.These fragmental ions were attributed to the direct dissociation of the parent ions.Electronic structurecalculations were also carried out with Hartree-Fock,density functional and correlated levels of theory to under-stand the possible fragmentation pathways.The very low N-Cl bond energy in the parent ion of nitrosyl chloride isa clear reason for the absence of ClNO~ and ClN~ ion peaks from the femtosecond laser mass spectrum. 相似文献
78.
The concentration fields, Nusselt number distributions along the electrode, and ratios of concentrations of electrochemically active components at the entrance into and exit out of an electrochemical cell are determined by numerical integration of the convective-diffusion equation for a broad range of rate constants of electrode reactions, Peclet numbers, and geometrical parameters of channels. Three regions of parameter values are revealed. At low reaction rates (K
l
< 0.5), mass transfer is completely determined by electrode kinetics; at high rates (K
l
> 20), it is completely determined by the diffusion in the gas phase; and in the intermediate region of values of K
l
it is necessary to allow for both the diffusion processes and the electrode reactions.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 317–324.Original Russian Text Copyright © 2005 by Ezin, Somov. 相似文献
79.
From the changes in energy band, density of state (DOS) and electronic structure calculated by the DFT/B3LYP method, the conductivity of carbon doped boron‐nitride nanotube (BNNT), which is formed by C‐C bond substituting B‐N bond, was discussed. The results indicate that the substitution will strengthen the conductivity of the tube, and its semi‐conductivity might be adjusted by controlling the substitution. 相似文献
80.
近年来,实验发现钛酸铅基材料具有负热膨胀性,且其热膨胀程度会受到掺杂元素的影响. 目前所研究的A位掺杂体系中,仅Cd原子掺杂能使钛酸铅负热膨胀性增强. 所以研究A位掺杂钛酸铅,比较Cd原子与其他原子在掺杂钛酸铅时化学键的异同,有助于深刻理解钛酸铅负热膨胀的本质. 本文利用第一性原理,分别优化了Sr、Ba、Cd掺杂钛酸铅的晶格常数,计算了它们的态密度和电荷密度. 结果表明Cd―O键的共价性强于Pb―O键,而Ba―O键和Sr―O键几乎呈离子性,Ba/Sr对Pb的替代削弱了化合物的共价性,降低了自发极化强度. 与实验测量的热膨胀系数对比可以发现,A位原子与氧原子之间的共价性增强,化合物负热膨胀程度升高;若A位原子与氧原子之间的共价性削弱,负热膨胀程度降低. 可见A位原子与氧原子之间的共价性影响了钛酸铅基化合物负热膨胀性. 相似文献