A First-Principles Study of Pd-Pt Nanoclusters and their Hydrogen Adsorption Properties

2012 ◽  
Vol 1446 ◽  
Author(s):  
Teck L. Tan ◽  
Kewu Bai
Keyword(s):  
Particle Size ◽  
First Principles ◽  
Hydrogen Adsorption ◽  
Surface Adsorption ◽  
Expansion Method ◽  
Pt Nanoclusters ◽  
Cluster Expansion Method ◽  
Pt Alloy ◽  
Effect Of Particle Size ◽  
Adsorption Energies

ABSTRACTTo demonstrate the effects of particle size and alloying on hydrogen adsorption on metals, we explore stable configurations of Pd-Pt alloy using a 55-atom cubo-octahedron. Via first-principles based cluster expansion method, we obtained groundstate configurations and show how their hydrogen adsorption energies change with Pd-Pt composition. Comparison with surface adsorption energies further shows the effect of particle size.

scholarly journals First-Principles Atomistic Thermodynamics and Configurational Entropy

2020 ◽  
Vol 8 ◽  
Author(s):  
Christopher Sutton ◽  
Sergey V. Levchenko
Keyword(s):  
First Principles ◽  
Configurational Entropy ◽  
Functional Materials ◽  
Expansion Method ◽  
Bulk Materials ◽  
Cluster Expansion Method ◽  
Particle Exchange ◽  
Properties Of Materials ◽  
Atomistic Thermodynamics ◽  
Statistical Effects

In most applications, functional materials operate at finite temperatures and are in contact with a reservoir of atoms or molecules (gas, liquid, or solid). In order to understand the properties of materials at realistic conditions, statistical effects associated with configurational sampling and particle exchange at finite temperatures must consequently be taken into account. In this contribution, we discuss the main concepts behind equilibrium statistical mechanics. We demonstrate how these concepts can be used to predict the behavior of materials at realistic temperatures and pressures within the framework of atomistic thermodynamics. We also introduce and discuss methods for calculating phase diagrams of bulk materials and surfaces as well as point defect concentrations. In particular, we describe approaches for calculating the configurational density of states, which requires the evaluation of the energies of a large number of configurations. The cluster expansion method is therefore also discussed as a numerically efficient approach for evaluating these energies.

scholarly journals Anion order in perovskite oxynitrides AMO2N (A = Ba, Sr, Ca; M = Ta, Nb): a first-principles based investigation

RSC Advances ◽  
2020 ◽  
Vol 10 (41) ◽  
pp. 24410-24418
Author(s):  
Xi Xu ◽  
Hong Jiang
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Cluster Expansion ◽  
First Principles ◽  
Expansion Method ◽  
First Principles Calculations ◽  
Cluster Expansion Method

Anion order in perovskite oxynitrides is investigated by a combination of first-principles calculations, cluster expansion method and Monte Carlo simulations.

Electronic structure of molecular hydrogen in MoS2 nanopores

2021 ◽  
Author(s):  
Murilo Kendjy ◽  
Andreia Luisa da Rosa ◽  
Th. Frauenheim
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Molecular Hydrogen ◽  
High Selectivity ◽  
Hydrogen Adsorption ◽  
Gas Sensing ◽  
First Principles Calculations ◽  
Dna Translocation ◽  
Metallic Behavior ◽  
Adsorption Energies

Abstract Atom controlled sub-nanometer MoS2 pores have been recently fabricated with promising applications, such gas sensing, hydrogen storage and DNA translocation. In this work we carried out first-principles calculations of hydrogen adsorption in tiny MoS2 nanopores. Some of the pores show metallic behavior whereas others have a sizeable band gap. Whereas adsorption of molecular hydrogen on bare pores are dominated by physisorption, adsorption in the nanopores show chemisorption behavior with high selectivity depending on the pore inner termination. Finally, we show that functionalization with copper atoms leads to does not improve dignificantly the adsorption energies of selected pores.selected pores.

First-Principles Study of Formation and Properties of Fcc-NdOx in Nd-Fe-B Sintered Magnets

2010 ◽  
Vol 654-656 ◽  
pp. 1674-1677 ◽  
Author(s):  
Ying Chen ◽  
Satoshi Hirosawa ◽  
Shuichi Iwata
Keyword(s):  
Oxygen Concentration ◽  
First Principles ◽  
Formation Energy ◽  
Expansion Method ◽  
Sintered Magnets ◽  
Interfacial Phase ◽  
Cluster Expansion Method ◽  
Ordered Phases ◽  
Fcc Phase ◽  
The Stability

The NdOx phase formed at the Nd/Nd-Fe-B interface in Nd-sputtered Nd-Fe-B sintered magnets is paid rather attention recently due to its important role in coercivity generation of surface Nd-Fe-B grains. Its crystal structures have been reported to vary with the change of the oxygen concentration, and the disorder fcc phase derived from Nd2O3-C-type structure to be the main form of existence. To understand the formation mechanism of this fcc-NdOx interfacial phase, the stability of all oxygen concentration range of Nd-O system has been investigated from the first principles. Based on LSDA+U calculations for selected ordered phases at various oxygen concentration in Nd-O, the Cluster Expansion Method (CEM) is applied to evaluate the formation energy, density of states and other properties of disorder phase.

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