scholarly journals Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

2014 ◽  
Vol 4 (9) ◽  
pp. 2797-2813 ◽  
Author(s):  
Céline Chizallet ◽  
Pascal Raybaud
Keyword(s):  
Density Functional Theory ◽  
Amorphous Silica ◽  
Density Functional ◽  
Surface Model ◽  
Functional Theory ◽  
Catalytic Materials ◽  
Platinum Particles ◽  
Silica Alumina ◽  
Low Coverage ◽  
The Ideal

Advanced DFT models of complex catalysts, such as amorphous silica–alumina and supported subnanometric platinum particles, bridge the gap between the ideal surface model and the industrial catalyst.

Theoretical determination of the structures of CaSiO3 perovskites

2006 ◽  
Vol 62 (6) ◽  
pp. 1025-1030 ◽  
Author(s):  
Razvan Caracas ◽  
Renata M. Wentzcovitch
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Determination ◽  
Functional Theory ◽  
Starting Point ◽  
Atomic Coordinates ◽  
The Ideal

Density functional theory is used to determine the possible crystal structure of the CaSiO3 perovskites and their evolution under pressure. The ideal cubic perovskite is considered as a starting point for studying several possible lower-symmetry distorted structures. The theoretical lattice parameters and the atomic coordinates for all the structures are determined, and the results are discussed with respect to experimental data.

Density Functional Theory Study of H2O Molecules on Cr2O3 Surfaces

2014 ◽  
Vol 783-786 ◽  
pp. 2172-2175
Author(s):  
Norio Nunomura ◽  
Satoshi Sunada
Keyword(s):  
Density Functional Theory ◽  
Oxygen Atom ◽  
Density Functional ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Molecular Plane ◽  
Absorption Energy ◽  
Low Coverage ◽  
Good Agreement ◽  
Surface Oxygen Atom

In order to understand the reactivity of Cr2O3 surface towards H2O molecule, the optimized structure, electronic structure, and the behavior of adsorbates were examined using a first-principles calculation based on density-functional theory (DFT). H2O coverages varying from a quarter to two monolayers (MLs) were considered. At a low coverage, the oxygen atom of H2O adsorbs on the Cr atom of the outermost Cr2O3 surface layer, the entire H2O molecule is slanted at the direction of a hollow site, and a molecular plane is nearly parallel to the surface. The hydrogen bond is formed between the surface oxygen atom and the hydrogen atom of H2O molecule. From the optimized structure, the H2O dissociation mechanism which passes through a transition state is guessed. For 0.5ML coverage the obtained absorption energy is-82.5 kJ/mol. Our results are in good agreement with other reported theoretical and experimental results.

scholarly journals An Experimental and Theoretical Study of Dye Properties of Thiophenyl Derivatives of 2-Hydroxy-1,4-naphthoquinone (Lawsone)

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5587
Author(s):  
Matías Monroy-Cárdenas ◽  
Oscar Forero-Doria ◽  
Ramiro Araya-Maturana ◽  
Maximiliano Martínez-Cifuentes
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Dye Sensitized Solar Cells ◽  
Nbo Analysis ◽  
Surface Model ◽  
Excitation Energies ◽  
Absorption Bands ◽  
Functional Theory ◽  
Computational Calculations ◽  
A Prospective Study

A prospective study of the dye properties of non-toxic lawsone thiophenyl derivatives, obtained using a green synthetic methodology allowed for the description of their bathochromic shifts in comparison to those of lawsone, a well-known natural pigment used as a colorant that recently also has aroused interest in dye-sensitized solar cells (DSSC). These compounds exhibited colors close to red, with absorption bands in visible and UV wavelength range. The colorimetric study showed that these compounds exhibited a darker color than that of lawsone within a range of colors depending on the substituent in the phenyl ring. Computational calculations employing Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT), showed that the derivatives have lower excitation energies than lawsone, while the alignment of their frontier orbitals regarding the conduction bands of TiO2 and ZnO and the redox potential of the electrolyte I−/I3− suggests that they could be employed as sensitizers. The study of the interactions of the lawsone and a derivative with a TiO2 surface model by different anchoring modes, showed that the adsorption is thermodynamically favored. Natural bond orbital (NBO) analysis indicates a two-center bonding (BD) O-Ti as the main interaction of the dyes with TiO2.

scholarly journals Identification of an AgS2 Complex on Ag(110)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Peter M. Spurgeon ◽  
Da-Jiang Liu ◽  
Junepyo Oh ◽  
Yousoo Kim ◽  
Patricia A. Thiel
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Functional Theory ◽  
Adsorbed Sulfur ◽  
Low Coverage

AbstractAdsorbed sulfur has been investigated on the Ag(110) surface at two different coverages, 0.02 and 0.25 monolayers. At the lower coverage, only sulfur adatoms are present. At the higher coverage, there are additional bright features which we identify as linear, independent AgS2 complexes. This identification is based upon density functional theory (DFT) and its comparison with experimental observations including bias dependence and separation between complexes. DFT also predicts the absence of AgS2 complexes at low coverage, and the development of AgS2 complexes around a coverage of 0.25 monolayers of sulfur, as is experimentally observed. To our knowledge, this is the first example of an isolated linear sulfur-metal-sulfur complex.

scholarly journals Characterizing modulated structures with first-principles calculations: a unified superspace scheme of ordering in mullite

2019 ◽  
Vol 75 (2) ◽  
pp. 260-272 ◽  
Author(s):  
Paul Benjamin Klar ◽  
Iñigo Etxebarria ◽  
Gotzon Madariaga
Keyword(s):  
Phase Diagram ◽  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Complex Nature ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Modulated Structures ◽  
Total Energies ◽  
The Ideal

The benefit of computational methods applying density functional theory for the description and understanding of modulated crystal structures is investigated. A method is presented which allows one to establish, improve and test superspace models including displacive and occupational modulation functions from first-principles calculations on commensurate structures. The total energies of different configurations allow one to distinguish stable and less stable structure models. The study is based on a series of geometrically optimized superstructures of mullite (Al4+2x Si2−2x O10−x ) derived from the superspace group Pbam(α0½)0ss. Despite the disordered and structurally complex nature of mullite, the calculations on ordered superstructures are very useful for determining the ideal Al/Si ordering in mullite, extracting atomic modulation functions as well as understanding the SiO2–Al2O3 phase diagram. The results are compared with experimentally established models which confirm the validity and utility of the presented method.

CO-ADSORPTION CALCULATIONS OF CO AND H2O MOLECULES ON ATOMIC CU CLUSTER DEPOSITED ZNO SURFACE: A DENSITY FUNCTIONAL THEORY STUDY

2020 ◽  
Vol 27 (03) ◽  
Author(s):  
VO THANH CONG ◽  
QUY DIEM DO ◽  
PHAM THANH TAM ◽  
VAN THANH KHUE ◽  
PHAM VAN TAT
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Co Adsorption ◽  
Surface Model ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Copper Clusters ◽  
Adsorption Of Co ◽  
Insight Into

Calculations of adsorption and reaction mechanism on ZnO  surface have been investigated. In this work, the deposition of six atomic copper clusters (6Cu) on ZnO  surface (called 6Cu/ZnO  model), using density functional theory was employed to calculate for CO and H2O co-adsorption. In performance, on ZnO  surface, 6Cu were adsorbed to obtain four stable sites of 6Cu/ZnO model, called as 6Cu-I, 6Cu-II, 6Cu-III, and 6Cu-IV. The calculated results found that the 6Cu-IV was the most stable surface model, thus, used to examine the co-adsorption of CO and H2O molecules. Further, CO and H2O co-adsorption on ZnO  surface were calculated also to compare with 6Cu/ZnO surface. Based on co-adsorption energy calculations indicated that CO and H2O co-adsorption on 6Cu/ZnO surface were more favorable than on ZnO  surface. The studied results will provide an insight into the effective adsorption of cluster on ZnO-based surface by deposition.

Interaction of CO with Pd-Doped α-Fe2O3 (001) in the CLC System: A Density Functional Analysis

2011 ◽  
Vol 403-408 ◽  
pp. 2285-2288 ◽  
Author(s):  
Wu Qin ◽  
Qiu Luan Chen ◽  
Tie Cheng Wang ◽  
Ning Wang ◽  
Wen Yan Li ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Functional Analysis ◽  
Surface Layer ◽  
Active Sites ◽  
Density Functional ◽  
Theoretical Interpretation ◽  
Functional Theory ◽  
System A ◽  
Adsorption Of Co ◽  
The Ideal

The present work is devoted to the theoretical interpretation of interaction of CO molecule with Pd-doped α-Fe2O3(001) using density functional theory (DFT). Two doping types were taken into account, which either a pair of Fe atoms of α-Fe2O3(001) surface was replaced by Pd or a pair of Pd atoms embedded into the vacancy between surface layer and sub-surface layer of α-Fe2O3(001). Three different active sites of the α-Fe2O3(001) surface and the Pd-doped α-Fe2O3(001) surface were considered for the interaction between CO and these surfaces. We found that the binding energy of CO on Pd-doped α-Fe2O3(001) surface was much more than that of the clean α-Fe2O3(001) surface. Results indicated metallic atoms are a Subscript text ctive site for adsorption of CO molecule, and the S(001) while interaction between CO molecule and surface doped by replacing Fe atom with Pd atom, stronger interaction happen between CO molecule and Pd embedded-doped α-Fe2O3(001) surface than that between CO molecule and the ideal surface, leading to the formation of CO2precursor species.

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