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Bonding Character and Formation Energy of Point Defects of He and Vacancy on (001) Surface of bcc Iron by First Principle Calculations

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Acta Metallurgica Sinica(English Letters) 2013年第1期26卷 25-32页

作者： Jun CAI Daogang LU School of Nuclear Science and Engineering North China Electric Power University

The structure and energy of He impurities and vacancy on （001） surface of bcc iron are investigated by an ab initio method. Three cases for stabilities of a He atom at the surface are found： some of He atoms at surface atomic layers （SAL） relax into vacuum gap; some of surface He atoms at octahedral interstitial site relax into more stable tetrahedral interstitial site; some of surface He atoms still stay at tetrahedral interstitial site. The un-stability of the He atom at the surface system can be explained by deformation mechanism of charge densities and electronic densities of states. It is found that formation energy of the point defects from the topmost SAL to bulk-like atomic layer increase gradually, for example, the formation energies of a monovacancy at the first five topmost SALs are equal to 0.33, 1.56, 2.04, 2.02 and 2.11 eV, respectively. The magnetic moments of Fe atoms in the surface atomic layers are also calculated.

关键词： ab initio calculations Single point defects bcc Fe (001) surface electronicstructure

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Theoretical Study on Electronic Gain-and-loss Properties of TEMPO and Its Derivates in Charge/Discharge Processes

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Chinese Journal of Chemical Physics 2012年第2期25卷 161-168,I0003页

作者： Shu-cai Mao Jin-qing Qu Kang-cheng Zheng School of Chemistry and Chemical Engineering Zhongkai University of Agriculture and EngineeringGuangzhou 510225China School of Chemistry and Chemical Engineering South China University of TechnologyGuanEzhou 510640China School of Chemistry and Chemical Engineering Sun Yat-Sen UniversityGuangzhou 510275China

Theoretical study on the electronic structures and related properties of 2,2,6,6-tetramethyl- l-piperidinyloxy （TEMPO） and its cationic lipid derivates in the charge/discharge processes has been carried out using the density functional theory （DFT） at the （U）B3LYP/6-31G（d,p） or 6-31＋G（d,p） level. The changes and regularities of geometric and electronic properties of these compounds in the charge/discharge processes were revealed in detail. The compu- tational results show that the substitute group plays a very important role in the electronic structures and related properties of TEMPOs during the charge/discharge processes. It is very interesting to find that after getting an electron, TEMPO is more stable in singlet state but the lipid is more stable in triplet state. For TEMPO, both the charge and the discharge processes greatly influence the electronic properties of N and O atoms of the radical part. For the cationic lipid, the discharge process mainly influences the pyridinium head and the charge process mainly influences the free radical head. Moreover, the solvent effect plays an important role in some bond lengths and the charge population of the free radical head. In addition, the UV-Vis absorption spectra simulated using TDDFT at the 6-31G（d,p） with the experimental ones. of TEMPO and the lipid were calculated and or 6-31＋G（d,p） level, in satisfying agreement

关键词： 2,2,6,6-tetramethyl-l-piperidinyloxy Charge/discharge process electronicstructure Density functional theory calculation

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Catalytic activity of noble metal nanoparticles toward hydrodechlorination： influence of catalyst electronic structure and nature of adsorption

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Frontiers of Environmental Science & Engineering 2015年第5期9卷 888-896页

作者： Man ZHANG Feng HE Dongye ZHAO Department of Civil Engineering Auburn University Auburn AL 36849 USA College of Biological and Environmental Engineering Zhejiang University of Technology Hangzhou 310014 China

In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose （CMC） as a capping agent. These metal nanoparticles were then tested for catalytic hydrodechlorination toward two classes of organochlorinated compounds （vinyl polychlorides includ- ing trichloroethylene （TCE）, tetrachloroethylene （PCE）, and alkyl polychlorides including 1,1,1-trichloroethane （1,1,1-TCA）, and 1,1,1,2-tetrachloroethane （1,1,1,2- TeCA）） to determine the rate-limiting steps and to explore the reaction mechanisms. The surface area normalized reaction rate constant, ksA, showed a systematic depen- dence on the electronic structure （the density of states at the Fermi level） of the metals, suggesting that adsorption of organochlorinated reactants on the metal catalyst surfaces is the rate-limiting step for catalytic hydrodechlorination. Hydrodechlorination rates of 1,1,1-TCA and 1,1,1,2-TeCA agreed with the bond strength of the first （weakest） dissociated C-C1 bond, suggesting that C-C1 bond cleavage, which is the first step for dissociative adsorption of the alkyl polychlorides, controlled the catalytic hydro- dechlorination rate. However, hydrodechlorination rates of TCE and PCE correlated with the adsorption energies of their molecular （non-dissociative） adsorption on the noble metals rather than with the first C-C1 bond strength, suggesting that molecular adsorption governs the reaction rate for hydrodechlorination of the vinyl polychlorides.

关键词： catalytic hydrodechlorination electronicstructure metal nanoparticles reaction mechanisms

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