Structure of Chromium Atomic Chains

2011 ◽  
Vol 415-417 ◽  
pp. 553-556 ◽  
Author(s):  
Han Xin Shen ◽  
Wen Zhang Zhu ◽  
Ai Yu Li
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Electronic Energy ◽  
Present Calculation ◽  
Energy Bands ◽  
One Dimensional ◽  
Atomic Chains ◽  
Calculation Results ◽  
Electronic Energy Bands

The geometric and electronic structures of Cr chains are studied by the first-principles of density-functional method. The present calculation results show that chromium can form planar chains in linear, zigzag, dimer, and ladder form one-dimensional structures. The most stable geometry chain among the studied structures is the ladder-form chain with five nearest neighbors. The dimer structure is found to be more stable than the zigzag one. Further more, the relative structural stability, the electronic energy bands, the density of states is discussed based on the ab initio calculations.

Spatial Configurations of Molybdenum Atomic Chains

2011 ◽  
Vol 366 ◽  
pp. 447-450
Author(s):  
Han Xin Shen ◽  
Wen Zhang Zhu ◽  
Ai Yu Li
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Electronic Energy ◽  
Energy Bands ◽  
Ladder Structure ◽  
Atomic Chains ◽  
Spatial Configurations ◽  
Electronic Energy Bands

The geometric and electronic structures of Molybdenum chains are studied by the first-principles of density-functional method. The present calculations reveal that Molybdenum can form planner chains in zigzag, dimer, and ladder structures. The most stable geometry is the Dimer structure chain. The ladder structure is found to be more stable than the zigzag one. Furthermore, the relative structural stability, the electronic energy bands, the density of states are discussed based on the ab initio calculations.

First Principles Calculations of Electronic and Optical Properties of Al1-xLaxN

2011 ◽  
Vol 393-395 ◽  
pp. 110-113
Author(s):  
Chang Peng Chen ◽  
Mei Lan Qi
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Density Functional Method ◽  
High Energy ◽  
Functional Method ◽  
Absorption Region ◽  
Additional Absorption ◽  
Calculation Results ◽  
La Substitution

Based on the density functional method, the electronic structures and the optical properties for Al1-xLaxN(x=0, 0.0625, 0.125, 0.1875) are comparatively investigated in detail. The calculation results indicate that La substitution of the Al sites induces effective reduction of the band gap of AlN, and the band gap being continuously reduced when increasing La doping level. With the increase of La concentration, both the imaginary part of dielectric function and the absorption spectrum show red-shift corresponding to the change of band gaps. Moreover, additional absorption peaks are observed above the absorption edge in the high-energy range which widens the absorption region.

Electronic Structure and Optical Properties of La or In Doped SnO2: First-Principles Calculations

2011 ◽  
Vol 393-395 ◽  
pp. 80-83
Author(s):  
Chang Peng Chen ◽  
Mei Lan Qi
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
First Principles Calculations ◽  
Effective Reduction ◽  
Calculation Results ◽  
Impurity Elements

Based on the density functional method, the electronic structures and the optical properties for pure and La or In doped SnO2 are comparatively investigated in detail. The calculation results indicate that both the doping of La and the doping of In induce effective reduction of the band gap of SnO2, the impurity elements form new highly localized impurity energy level at the top of the valence band near the Fermi level. The interaction between electrons changed after doping which leads to the change of electrical properties .Meanwhile, red shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change of band gaps

Theoretical Investigations of the Mechanism of CO2-CH4 Reforming Reaction Catalyzed by Transition Metals (Pt, Rh, Ru) under a Supercritical Condition

2013 ◽  
Vol 291-294 ◽  
pp. 795-798 ◽  
Author(s):  
Wen Yuan Xu ◽  
Na Na Xu ◽  
Wei Long ◽  
Lin Hu ◽  
San Guo Hong
Keyword(s):  
Transition Metals ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Transition Metal Catalysts ◽  
Supercritical Condition ◽  
Energy Calculation ◽  
Rate Determining Step ◽  
Theoretical Investigations ◽  
Calculation Results

A mechanism of CO2-CH4 reforming over supported transition metal catalysts (platinum, rhodium, ruthenium) under a supercritical condition (304.13K, 72.90atm) was investigated using the B3LYP density functional method and MP2 method. Results obtained show that there are two channels in this reaction. The oxidized material is the most important catalyst in each reaction channel. For Pt, Rh and Ru, the rate-determining step of the reaction is the same - the step of CO2 activation. Because of the large activation energies, the oxide reforming on Rh and Ru catalysts can't proceed under the supercritical condition. For Pt, the CO2 activation reaction proceeds easier than the other two kinds of catalysts. According to the energy calculation results, specific activities of three kinds of the transition metals follow in the order: Pt ＞ Rh ＞ Ru.

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