REACTION PATH FOR THE DISSOCIATIVE ADSORPTION OF HYDROGEN ON THE (100) SURFACES OF FACE-CENTERED-CUBIC TRANSITION METALS

1997 ◽  
Vol 04 (06) ◽  
pp. 1347-1351 ◽  
Author(s):  
A. EICHLER ◽  
J. HAFNER ◽  
G. KRESSE
Keyword(s):  
Density Functional ◽  
Noble Metals ◽  
Reaction Path ◽  
Local Density ◽  
Chemical Reactivity ◽  
Dissociative Adsorption ◽  
Face Centered Cubic ◽  
Hydrogen Molecules ◽  
Adsorption Of Hydrogen ◽  
Face Centered

Detailed ab-initio local-density-functional studies of the potential-energy surfaces for the dissociative adsorption of hydrogen molecules on the (100) surfaces of face-centered-cubic transition and noble metals are presented. We show that the energetically most favorable reaction path is determined by quantum-mechanical steering effects arising from the formation and modification of covalent metal–hydrogen bonds. Variations of the local chemical reactivity with the filling of the d-band are discussed at the example of rhodium, palladium and silver surfaces.

Density Functional Theory Study of Influence of Hydrogen Absorption on the Field Emission Properties of Carbon Nanotubes

2011 ◽  
Vol 306-307 ◽  
pp. 1166-1169
Author(s):  
Kai Sun ◽  
Zhi Qin Fan ◽  
Xiu Ying Liu
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional Theory ◽  
Field Emission ◽  
Density Functional ◽  
Local Density ◽  
Functional Theory ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Hydrogen Molecules ◽  
Adsorption Of Hydrogen

The field-emission properties of capped(5, 5) single-walled carbon nanotubes with hydrogen adsorbed on the tip with and without an applied electric field have been investigated using first-principles density-functional theory. It is found that the structure of carbon nanotubes with hydrogen molecules is stable under field-emission conditions. The local density of states at the Fermi level increases with the adsorption of hydrogen molecules. These results elucidate that the field-emission properties of carbon nanotubes can be enhanced by the adsorption of hydrogen molecules, and are consistent with the experimental results.

Equilibrium Structure and Schottky Barriers at Eras/Gaas Interfaces

1997 ◽  
Vol 492 ◽  
Author(s):  
A. G. Petukhov ◽  
B. T. Hemmelman ◽  
W. R. L. Lambrecht
Keyword(s):  
Local Density ◽  
Equilibrium Structure ◽  
Schottky Barriers ◽  
Orbital Method ◽  
Full Potential ◽  
Face Centered Cubic ◽  
Erbium Arsenide ◽  
Self Energy ◽  
Ideal Situation ◽  
Face Centered

ABSTRACTThe equilibrium structures as well as the electronic Schottky barriers for (100) Erbium-Arsenide/Gallium-Arsenide (ErAs/GaAs) arsenic and gallium terminated interfaces have been determined by ab-initio calculations using the local-density approximation and a full-potential linear-muffin-tin-orbital method. In both cases the arsenic sublattice was chosen to be continuous across the interface in accordance with experiments on Rutherford backscattering channeling. Band structures, densities of states, and charge density distributions were also determined for the interfaces. The comparison of the total supercell energies reveals that the gallium terminated (chain) interface is more energetically stable than the arsenic terminated (shadow) interface. It also shows that the equilibrium interface separation for the arsenic terminated interface corresponds to an ideal structure when arsenic forms undistorted face-centered cubic lattice. The separation in the gallium terminated interface is quite substantial and is 60% larger than that of the ideal situation. The model also predicts that no buckling of the ErAs interface monolayer will occur for either structure. The computed Schottky barriers for holes (after a semi-empirical quasiparticle self-energy correction) are 0.6 eV for the chain interface and 0.4 eV for the shadow interface.

Nature of Non-magnetic Strongly-Correlated State in Plutonium

2006 ◽  
Vol 986 ◽  
Author(s):  
Leniod Purovskii ◽  
Alexander Shick ◽  
Ladislav Havela ◽  
Mikhail Katsnelson ◽  
Alexander Lichtenstein
Keyword(s):  
Field Theory ◽  
Density Functional ◽  
Local Density ◽  
Mean Field Theory ◽  
Mean Field ◽  
Dynamical Mean Field Theory ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Strongly Correlated ◽  
Starting Point

AbstractLocal density approximation for the electronic structure calculations has been highly successful for non-correlated systems. The LDA scheme quite often failed for strongly correlated materials containing transition metals and rare-earth elements with complicated charge, spin and orbital ordering. Dynamical mean field theory in combination with the first-principle scheme (LDA+DMFT) can be a starting point to go beyond static density functional approximation and include effects of charge, spin and orbital fluctuations. Ab-initio relativistic dynamical mean-field theory is applied to resolve the long-standing controversy between theory and experiment in the “simple” face-centered cubic phase of plutonium called δ-Pu. In agreement with experiment, neither static nor dynamical magnetic moments are predicted. In addition, the quasiparticle density of states reproduces not only the peak close to the Fermi level, which explains the large coefficient of electronic specific heat, but also main 5f features observed in photoelectron spectroscopy.

scholarly journals Relativistic Effects on the Equation-of-State of the Light Actinides

2005 ◽  
Vol 893 ◽  
Author(s):  
Alexander Landa ◽  
Per Söderlind
Keyword(s):  
Electronic Structure ◽  
Equation Of State ◽  
Density Functional ◽  
Relativistic Effects ◽  
Model Systems ◽  
Face Centered Cubic ◽  
Electronic Structure Methods ◽  
The Face ◽  
Face Centered ◽  
Structure Calculations

AbstractThe effect of the relativistic spin-orbit (SO)interaction on the bonding in the early actinides has been investigated by means of electronic-structure calculations. Specifically, the equation of state (EOS) for the face-centered cubic (fcc) model systems of these metals has been calculated from the first-principles density-functional (DFT) theory. Traditionally, the SO interaction in electronic-structure methods is implemented as a perturbation to the Hamiltonian that is solved for basis functions that explicitly do not depend on SO coupling. Here this approximation is shown to compare well with the fully relativistic Dirac treatment. It is further shown that SO coupling has a gradually increasing effect on the EOS as one proceeds through the actinides and the effect is diminished as density increases.

Structural and Electronic Properties of Hydrogen-Passivated Silicon Quantum Dots: Density Functional Calculations

2015 ◽  
Vol 1107 ◽  
pp. 571-576 ◽  
Author(s):  
Muhammad Mus-'ab Anas ◽  
Ahmad Puaad Othman ◽  
Geri Gopir
Keyword(s):  
Quantum Dots ◽  
Density Functional ◽  
Energy Gap ◽  
Local Density ◽  
Basis Set ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Silicon Quantum Dots ◽  
Theoretical Approaches ◽  
Passivated Silicon

Density functional theory (DFT) by numerical basis-set calculations of silicon quantum dots (Si-QDs) passivated by hydrogen, ranging in size up to 1.9 nm are presented. These DFT computation results are used to examine and deduce the properties of 14 spherical Si-QDs including its density of state (DOS), and energy gap from the HOMO-LUMO results. The atomistic model of each silicon QDs was constructed by repeating crystal unit cell of face-centered cubic (FCC) structure, then the QDs surface was passivated by hydrogen atoms. The model was relaxed and optimized using Quasi-Newton method for each size of Si-QDs to get an ideal structure. Exchange-correlation potential (Vxc) of electrons were approximated in this system using the Local Density Approximation (LDA) functional and Perdew-Zunger (PZ) functional. Finally, all results were compared with previous experimental data and other similar theoretical approaches, and these results augured well

scholarly journals Influence of Si Atoms Insertion on the Formation of the Ti-Si-N Composite by DFT Simulation

2016 ◽  
Vol 12 (23) ◽  
pp. 11-23
Author(s):  
Juan Manuel Gonzalez ◽  
Johans Steeven Restrepo ◽  
Carolina Ortega Portilla ◽  
Alexander Ruden Muñoz ◽  
Federico Sequeda Osorio
Keyword(s):  
Density Functional ◽  
Amorphous Matrix ◽  
Bond Formation ◽  
Crystalline Lattice ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Dft Simulation ◽  
Face Centered ◽  
Nano Grains ◽  
Fcc Structure

Using Density Functional Theory (DFT) SiN and TiN structures were simulated, in order to study the influence of the silicon atoms insertion in the TiN lattice placed on interstitial and substitutional positions in a face centered cubic (FCC) crystalline lattice. Results showed that the SiN - FCC structure is pseudo-stable; meanwhile the tetragonal structure is stable with ceramic behavior. The TiN - FCC structure is stable with ceramic behavior similar to SiN - Tetragonal. 21% silicon atoms insertion in interstitial positions showed high induced deformation, high polarization and Si - N bond formation, indication an amorphous transition that could lead to the production of a material composed from TiN grains or nano-grains embedded in a Si - N amorphous matrix. When including 21% of silicon atoms, substituting titanium atoms, the distribution showed higher stability that could lead to the formation of different phases of the stoichiometric Ti1 -x SixNy compound.

scholarly journals Looking Beyond Adsorption Energies to Understand Interactions at Surface Using Machine Learning

2021 ◽  
Author(s):  
Sheena Agarwal ◽  
Kavita Joshi
Keyword(s):  
Machine Learning ◽  
Small Molecules ◽  
Density Functional ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Full Picture ◽  
Adsorption Energies ◽  
Face Centered

Abstract<br>Identifying factors that influence interactions at the surface is still an active area of research. In this study, we present the importance of analyzing bondlength activation, while interpreting Density Functional Theory (DFT) results, as yet another crucial indicator for catalytic activity. We studied the<br>adsorption of small molecules, such as O 2 , N 2 , CO, and CO 2 , on seven face-centered cubic (fcc) transition metal surfaces (M = Ag, Au, Cu, Ir, Rh, Pt, and Pd) and their commonly studied facets (100, 110, and 111). Through our DFT investigations, we highlight the absence of linear correlation between adsorption energies (E ads ) and bondlength activation (BL act ). Our study indicates the importance of evaluating both to develop a better understanding of adsorption at surfaces. We also developed a Machine Learning (ML) model trained on simple periodic table properties to predict both, E ads and BL act . Our ML model gives an accuracy of Mean Absolute Error (MAE) ∼ 0.2 eV for E ads predictions and 0.02 Å for BL act predictions. The systematic study of the ML features<br>that affect E ads and BL act further reinforces the importance of looking beyond adsorption energies to get a full picture of surface interactions with DFT.<br>

DECOMPOSITION OF SiH4 ON THE SA TYPE STEPPED Si(100) SURFACE

2002 ◽  
Vol 09 (03n04) ◽  
pp. 1401-1407 ◽  
Author(s):  
ŞENAY KATIRCIOĞlu ◽  
ŞAKIR ERKOÇ
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Atom ◽  
Density Functional ◽  
Reaction Path ◽  
Density Functional Theory Method ◽  
Dissociative Adsorption ◽  
Theory Method ◽  
Functional Theory ◽  
Initial Stage ◽  
The Density Functional Theory

The density functional theory method is used to explore the mechanism of dissociative adsorption of silane (SiH4) on the SA type stepped Si(100) surface. Two reaction paths are described that produce silyl (SiH3) and hydrogen atom fragments adsorbed on the dimer bonds present on each terrace. It has been found that the initial stage of the dissociation of SiH4 on the SA type stepped Si(100) surface shows similarity to the dissociation of SiH4 on the flat Si(100) surface; SiH3 and hydrogen fragments bond to the Si dimer atoms by following the first reaction path.

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