ENHANCED SCREENING OF CORE HOLES AT TRANSITION-METAL SURFACES

1995 ◽  
Vol 02 (02) ◽  
pp. 197-201 ◽  
Author(s):  
M. METHFESSEL ◽  
D. HENNIG ◽  
M. SCHEFFLER
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Density Functional ◽  
Core Level ◽  
Level Shift ◽  
Core Hole ◽  
Initial State ◽  
Functional Theory ◽  
Level Shifts

Ab initio calculations based on density-functional theory were used to obtain surface core-level shifts for the 4d transition metals and silver in the initial-state model and in the full-impurity formulation, giving an unambiguous separation into initial state and screening terms. This shows that the screening of the core hole is substantially better at the surface than in the bulk for a transition metal. For Ag, an opposite and even larger effect is found, showing the central role of d-electron screening in the surface core-level shift of the transition metals.

AB-INITIO CALCULATION OF THE INITIAL- AND FINAL-STATE EFFECTS ON CORE LEVEL SHIFTS AT TRANSITION METAL SURFACES

1993 ◽  
Vol 07 (01n03) ◽  
pp. 542-545
Author(s):  
D. HENNIG ◽  
M. METHFESSEL ◽  
M. SCHEFFLER
Keyword(s):  
Transition Metal ◽  
Core Level ◽  
Level Shift ◽  
Full Potential ◽  
Initial State ◽  
Final State ◽  
State Approximation ◽  
Transition Metal Surface ◽  
Lmto Method ◽  
Level Shifts

The surface core-level shift at a transition metal surface can be calculated in two different ways using the initial-state approximation or using a more involved approach which includes screening of the photo-created core hole. Our calculated results obtained using the full-potential LMTO method for the close packed surfaces of all 4d transition metals within the initial state picture can be well explained by standard arguments.

Core Level Shifts and Grain Boundary Cohesion

1998 ◽  
Vol 4 (S2) ◽  
pp. 766-767
Author(s):  
D. A. Muller
Keyword(s):  
Charge Transfer ◽  
Valence Band ◽  
Core Level ◽  
Level Shift ◽  
The Core ◽  
Metallic Interfaces ◽  
Level Shifts ◽  
Electron Energy Loss ◽  
Valence Band Width

The role of core level shifts at metallic interfaces has often been ignored in electron energy loss spectroscopy (EELS) even though very small changes in bond length can lead to large core level shifts. However, the popular interpretation of core level shifts as measures of charge transfer is highly problematic. For instance, in binary alloys systems, the core level shifts can be the same sign for both atomic constituents[l]. The simple interpretation would require that both atomic species had lost or gained charge. Further, the signs of the core level shifts can be opposite to those expected from electronegativity arguments[2]. A core level shift (CLS) is still possible, even when no charge transfer occurs. As illustrated in Fig. 1, if the valence band width is increased, the position of the center of the valence band with respect to the Fermi energy will change (as the number of electrons remains unchanged).

Ti and Zr Transition Metals Effect in the D03 Fe3Al by Ab Initio Study Approach

2014 ◽  
Vol 783-786 ◽  
pp. 1640-1645
Author(s):  
Jean Marc Raulot ◽  
S. Chentouf ◽  
T. Grosdidier ◽  
Hafid Aourag
Keyword(s):  
Molecular Dynamics ◽  
Transition Metals ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Molecular Dynamics ◽  
Effect Of Temperature ◽  
Site Preference ◽  
Functional Theory ◽  
Study Approach

The effect of the Ti and Zr transition metals on the D03-Fe3Al intermetallic compounds has been investigated by means of ab initio Pseudo Potentials numerical simulations based on Density Functional Theory. Two main issues will be addressed the understanding of the role of these two transition metals in terms of stability of the bulk at the light of their site preference in the D03-Fe3Al structure the behaviour of Ti and Zr transition metals in the sigma 5 (310) [001] grain boundary and their effect on the structural stability of this interface. An important issue when studying these aspects is to take into accounts the effect of temperature. This requires a molecular dynamics treatment of the atoms in the supercell. The technique known as ab initio molecular dynamics (AIMD) solves these problems by combining ‘on the fly’ electronic structure calculations with finite temperature dynamics. Thus, our study was conducted both using the conventional static ab initio calculations (0K) as well as by taking into account the effect of temperature (Ab Initio Molecular Dynamics).

FIRST PRINCIPLES STUDY OF EFFECT OF 3d TRANSITION METAL-DOPED ZINC OXIDE ON GAS SENSITIVITY

2007 ◽  
Vol 21 (24) ◽  
pp. 1585-1592
Author(s):  
ZHIYONG QIU ◽  
RI-ICHI MURAKAMI
Keyword(s):  
Zinc Oxide ◽  
Transition Metal ◽  
Transition Metals ◽  
Density Functional ◽  
Variation Method ◽  
Gas Sensitivity ◽  
Discrete Variation ◽  
Functional Theory ◽  
Doped Zno ◽  
Metal Doped

Two series models were developed in order to investigate the gas sensitivity of 3d transition metal-doped zinc oxide (ZnO) materials. Software based on a discrete variation method (DVM) within the framework of density functional theory was used to calculate the electronic structures of the models. It was possible to determine gas sensitivity using the calculated results, from which a relationship between electronic properties and gas sensitivity was formed. The results showed that doping the transition metals greatly affected the gas sensitivity of ZnO -based materials. The main effect was attributed to the change in carrier concentration. On the contrary, the doping of transition metals had a negligible effect on the mobility of ZnO -based materials. Titanium or iron doped- ZnO is thus expected to have the best gas sensitivity of all of the 3d transition metal-doped ZnO materials.

scholarly journals Theoretical Description of the Physical/chemical Contributions Determining the Stability of Transition-Metal Doped Phosphorene Nanosheets

2020 ◽  
Author(s):  
Sasha Gazzari ◽  
Kerry Wrighton-Araneda ◽  
Diego Cortes-Arriagada
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
Transition Metals ◽  
Density Functional ◽  
Theoretical Description ◽  
Energy Decomposition ◽  
Functional Theory ◽  
Physical Chemical ◽  
The Stability ◽  
Metal Doped

In this report, we explore the stability of doped-phosphorene nanosheets with first-row transition metals in the framework of density functional theory and by using a bonding characterization and energy decomposition analyses.

scholarly journals Predicting the Effect of Dopants on CO2 Adsorption on Transition Metal Carbides: Case Study on TiC (001)

2020 ◽  
Author(s):  
Marti Lopez ◽  
Francesc Vines ◽  
Michael Nolan ◽  
Frances Illas
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Density Functional ◽  
Transition Metal Carbide ◽  
Metal Carbides ◽  
Functional Theory ◽  
Late Transition Metals ◽  
Late Transition ◽  
Early Transition

Previous work has shown that doping the TiC(001) surface with early transition metals significantly affects CO<sub>2</sub> adsorption and activation which opens a possible way to control this interesting chemistry. In this work we explore other possibilities which include non-transition metals elements (Mg, Ca, Sr, Al, Ga, In, Si, Sn) as well as late transition metals (Pd, Pt, Rh, Ir) and lanthanides (La, Ce) often used in catalysis. Using periodic slab models with large supercells and state-of-the-art density functional theory (DFT) based calculations, we show that, in all the studied cases, CO<sub>2</sub> appears as bent and, hence, activated. However, the effect is especially pronounced for dopants with large ionic crystal radii. These can increase desorption temperature by up to 230K, almost twice the value predicted when early transition metals are used as dopants. However, a detailed analysis of the results shows that the main effect does not come from electronic structure perturbations but from the distortion that the dopant generates into the surface atomic structure. A simple descriptor is proposed that would allow predicting the effect of the dopant on the CO<sub>2</sub> adsorption energy in transition metal carbide surfaces without requiring DFT calculations.

Site Preference and Elastic Properties of 3d Transition Metals Alloying Addition in Ductility YAg Alloys

2012 ◽  
Vol 535-537 ◽  
pp. 1000-1004
Author(s):  
Yu Rong Wu ◽  
Wang Yu Hu ◽  
Long Shan Xu
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
Transition Metals ◽  
Elastic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Alloying Elements ◽  
Site Preference ◽  
Functional Theory

First-principles supercell calculations based on density functional theory were performed to study the site preference behavior and elastic properties of 3d (Ti-Cu) transition-metal elements in B2 ductility YAg alloy. It is found that Ti occupies the Y sublattice, while V, Cr, Co, Fe, Ni and Cu tend to substitute for Ag site. All alloying elements can decrease the lattice parameters of Y8Ag8, among which Y7Ag8Ti shows the largest change. Furthermore, the calculated elastic constants show that Cr, Fe, Co and Cu can improve the ductility of YAg alloy, and Y8Ag7Fe presents the most ductility among these alloy, while Ti and Ni alloying elements reduce the ductility of YAg alloy, especially, V transforms ductile into brittle for YAg alloy. In addition, both V and Ni can increase the hardness of YAg alloy, and Y8Ag7V is harder than Y8Ag7Ni.

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