Modeling of Steels and Steel Surfaces Using Quantum Mechanical First Principles Methods

2013 ◽  
Vol 762 ◽  
pp. 445-450
Author(s):  
Matti Alatalo ◽  
Heikki Pitkänen ◽  
Matti Ropo ◽  
Kalevi Kokko ◽  
Levente Vitos
Keyword(s):  
First Principles ◽  
Atomic Level ◽  
Single Atom ◽  
Quantum Mechanical ◽  
Bulk Alloy ◽  
Potential Approximation ◽  
Materials Modelling ◽  
Chemical Disorder ◽  
Steel Surfaces ◽  
Random Alloys

We describe recent progress in first principles materials modelling applied to iron alloys. First principles methods in general have proven to be an effective way of describing atomic level phenomena in solids. When applied to alloys with chemical disorder, however, the widely used supercell methods turn out to be impractical due to the vast variety of different possible configurations. This problem can be overcome using the coherent potential approximation (CPA), which enables the description of a multicomponent alloy in terms of an effective medium constructed in such a way that it represents, on the average, the scattering properties of the alloy. A bulk alloy, in the case of substitutional random alloys, can thus be described with a single atom while a slab is needed to describe surfaces. The exact muffin-tin orbitals (EMTO) method provides a first principles method that can be combined with the CPA in order to describe steels and other multicomponent alloys. We describe the EMTO-CPA method and provide examples of both bulk and surface properties that can be modelled with this method.

Effect of Nb on the Properties of Ti-Nb Random Alloys from First-Principles

2013 ◽  
Vol 747-748 ◽  
pp. 890-898 ◽  
Author(s):  
Min Jie Lai ◽  
Xiang Yi Xue ◽  
Cai Si Meng ◽  
Hong Chao Kou ◽  
Bin Tang ◽  
...  
Keyword(s):  
First Principles ◽  
Lattice Parameters ◽  
Potential Approximation ◽  
Β Phase ◽  
Ω Phase ◽  
Opposite Situation ◽  
Random Alloys ◽  
The Stability ◽  
Increasing Temperature ◽  
Nb Addition

The effect of Nb on the equilibrium lattice parameters and relative stability between β and ω phases of Ti1-xNbx (0 < x 0.4) random alloys as well as their mechanical properties in body-centered-cubic crystallographic phase was investigated using the exact muffin-tin orbitals method in combination with the coherent potential approximation. It has been found that the calculated lattice parameters of the β phase agree well with the experimental data. For ω phase, the value of a increases almost linearly with increasing Nb concentration, while the opposite situation presented for c/a. Both Nb addition and increasing temperature enhanced the stability of β phase relative to ω phase. The critical Nb concentration for the complete stabilization of β phase at 300 K, 673 K and 1273 K was 22 at.%, 17 at.% and 9 at.%, respectively. The polycrystalline bulk modulus B, Youngs modulus E and shear modulus G increased monotonously with Nb addition and reducing the Nb concentration below 30 at.% resulted in lower E compared to that of Ti-6Al-4V. The calculated G/B values demonstrate that the bcc Ti1-xNbx (0 < x 0.4) random alloys should be intrinsically ductile.

scholarly journals Electronic metal–support interaction modulates single-atom platinum catalysis for hydrogen evolution reaction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yi Shi ◽  
Zhi-Rui Ma ◽  
Yi-Ying Xiao ◽  
Yun-Chao Yin ◽  
Wen-Mao Huang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Structure Activity Relationship ◽  
Atomic Level ◽  
Single Atom ◽  
Activity Relationship ◽  
Support Interaction ◽  
Structure Activity ◽  
Metal Support Interaction ◽  
Metal Support

AbstractTuning metal–support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, the understanding of the structure–activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal–support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure–activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt–H/Pt–OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.

scholarly journals Regulating coordination number in atomically dispersed Pt species on defect-rich graphene for n-butane dehydrogenation reaction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xiaowen Chen ◽  
Mi Peng ◽  
Xiangbin Cai ◽  
Yunlei Chen ◽  
Zhimin Jia ◽  
...  
Keyword(s):  
Coordination Number ◽  
Density Functional ◽  
Activation Barrier ◽  
Density Functional Theory Calculation ◽  
Catalytic Performance ◽  
Atomic Level ◽  
Metal Nanoparticle ◽  
Single Atom ◽  
Nano Structure ◽  
Theory Calculation

AbstractMetal nanoparticle (NP), cluster and isolated metal atom (or single atom, SA) exhibit different catalytic performance in heterogeneous catalysis originating from their distinct nanostructures. To maximize atom efficiency and boost activity for catalysis, the construction of structure–performance relationship provides an effective way at the atomic level. Here, we successfully fabricate fully exposed Pt3 clusters on the defective nanodiamond@graphene (ND@G) by the assistance of atomically dispersed Sn promoters, and correlated the n-butane direct dehydrogenation (DDH) activity with the average coordination number (CN) of Pt-Pt bond in Pt NP, Pt3 cluster and Pt SA for fundamentally understanding structure (especially the sub-nano structure) effects on n-butane DDH reaction at the atomic level. The as-prepared fully exposed Pt3 cluster catalyst shows higher conversion (35.4%) and remarkable alkene selectivity (99.0%) for n-butane direct DDH reaction at 450 °C, compared to typical Pt NP and Pt SA catalysts supported on ND@G. Density functional theory calculation (DFT) reveal that the fully exposed Pt3 clusters possess favorable dehydrogenation activation barrier of n-butane and reasonable desorption barrier of butene in the DDH reaction.

First principles and machine learning based superior catalytic activities and selectivities for N2 reduction in MBenes, defective 2D materials and 2D π-conjugated polymer-supported single atom catalysts

2021 ◽  
Author(s):  
Mohammad Zafari ◽  
Arun S. Nissimagoudar ◽  
Muhammad Umer ◽  
Geunsik Lee ◽  
Kwang S. Kim
Keyword(s):  
Machine Learning ◽  
Nitrogen Fixation ◽  
First Principles ◽  
Conjugated Polymer ◽  
2D Materials ◽  
Single Atom ◽  
Vacancy Defects ◽  
Catalytic Activities ◽  
Polymer Supported ◽  
New Machine

The catalytic activity and selectivity can be improved for nitrogen fixation by using hollow sites and vacancy defects in 2D materials, while a new machine learning descriptor accelerates screening of efficient electrocatalysts.

scholarly journals Highly dispersed Pt atoms and clusters on hydroxylated indium tin oxide: A view from first-principles calculations

2021 ◽  
Author(s):  
Simran Kumari ◽  
Philippe Sautet
Keyword(s):  
Heterogeneous Catalysis ◽  
Metal Atom ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
First Principles ◽  
Catalytic Performance ◽  
Small Cluster ◽  
Single Atom ◽  
First Principles Calculations ◽  
Highly Dispersed

Supported single-atom and small cluster catalysts have become highly popular in heterogeneous catalysis. These catalysts can maximize the metal atom utilization while still showcasing superior catalytic performance. One of the...

Elastic anharmonicity of bcc Fe and Fe-based random alloys from first-principles calculations

2017 ◽  
Vol 95 (2) ◽  
Author(s):  
Xiaoqing Li ◽  
Stephan Schönecker ◽  
Jijun Zhao ◽  
Levente Vitos ◽  
Börje Johansson
Keyword(s):  
First Principles ◽  
First Principles Calculations ◽  
Random Alloys

First-principles screening of single transition metal atoms anchored on two-dimensional C9N4 for the nitrogen reduction reaction

2021 ◽  
Vol 23 (14) ◽  
pp. 8784-8791
Author(s):  
Qingling Meng ◽  
Ling Zhang ◽  
Jinge Wu ◽  
Shuwei Zhai ◽  
Xiamin Hao ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Transition Metal ◽  
First Principles ◽  
Reduction Reaction ◽  
Single Atom ◽  
Two Dimensional ◽  
Metal Atoms ◽  
Transition Metal Atoms ◽  
Catalytically Active ◽  
Single Transition

Theoretical screening of transition metal atoms anchored on monolayer C9N4 as highly stable, catalytically active and selective single-atom catalysts for nitrogen fixation.

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