A First-Principles Study of Hydrogen Desorption from High Entropy Alloy TiZrVMoNb Hydride Surface

The desorption behaviors of hydrogen from high entropy alloy TiZrVMoNb hydride surface have been investigated using the density functional theory. The (110) surface has been determined to be the most preferable surface for hydrogen desorption from TiZrVMoNb hydride. Due to the high lattice distortion and heterogeneous chemical environment in HEA hydride, hydrogen desorption from the HEA hydride surface is found to be complex. A comparison of molecular and atomic hydrogen desorption reveals that hydrogen prefers to desorb in atomic states from TiZrVMoNb hydride (110) surface rather than molecular states during the hydrogen desorption process. To combine as H2 molecules, the hydrogen atoms need to overcome attractive interaction from TiZrVMoNb hydride (110) surface. These results suggest that the hydrogen desorption on TiZrVMoNb hydride (110) surface is a chemical process. The presented results provide fundamental insights into the underlying mechanism for hydrogen desorption from HEA hydride surface and may open up more possibilities for designing HEAs with excellent hydrogen desorption ability.

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Ab Initio Study of Hydrogen Desorption from Hydrogenated Diamond (100) Surface

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.121-123.1119 ◽

2007 ◽

Vol 121-123 ◽

pp. 1119-1124

Author(s):

Feng Bin Liu ◽

Jia Dao Wang ◽

Da Rong Chen ◽

Bing Liu

Keyword(s):

Density Functional ◽

Hydrogen Desorption ◽

Stable Structure ◽

Ab Initio Study ◽

Generalized Gradient ◽

Reaction Heat ◽

Functional Theory ◽

Desorption Process ◽

Generalized Gradient Approximation ◽

The Density Functional Theory

By means of the density functional theory on the basis of generalized gradient approximation, the reaction paths of the dehydrogenation from the diamond (100) surface was deduced due to the reaction heat. Moreover, the most stable structure of the hydride diamond (100) surface was obtained. The results indicate that the dehydrogenation is easier to take place at the same C-C dimer and forms the parallel geometries. The parallel 1×1:1.5H, 2×1:H and parallel 2×1:0.5H are the intermediate products during the hydrogen desorption process, while, 2×1:H is the most stable structure of the hydride diamond (100) surfaces. The calculated reaction heat is in accordance with the experimental results.

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Anisotropically Nanostructured Silicon: A First-Principle Approach.

MRS Proceedings ◽

10.1557/proc-832-f10.8 ◽

2004 ◽

Vol 832 ◽

Author(s):

Yuri Bonder ◽

Chumin Wang

Keyword(s):

Experimental Data ◽

Density Functional ◽

First Principle ◽

Hydrogen Atoms ◽

Functional Theory ◽

Nanostructured Silicon ◽

Plane Anisotropy ◽

The Density Functional Theory ◽

The Difference ◽

Good Agreement

ABSTRACTOptical properties of birefringent porous-silicon layers are studied within the density functional theory. Starting from a (110)-oriented supercell of 32 silicon atoms, columns of atoms in directions [100] and [010] are removed and the dangling bonds are saturated with hydrogen atoms. The results show an in-plane anisotropy in the dielectric function and in the refractive index (n). The difference Δn defined as n[110] -n[001] is compared with experimental data and a good agreement is observed. Also, the possibility in determining the morphology of pores by using polarized lights is analyzed.

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Exploring the Relationship between the CO Oxidation Reaction and the Elemental Composition in Electrocatalysts with Machine Learning - a Case Study of PtRuPdRhAu High Entropy Alloys

10.33774/chemrxiv-2021-zpbqb-v3 ◽

2021 ◽

Author(s):

Vladislav Mints ◽

Jack Pedersen ◽

Alexander Bagger ◽

Jonathan Quinson ◽

Andy Anker ◽

...

Keyword(s):

Machine Learning ◽

Co Oxidation ◽

Oxidation Reaction ◽

Density Functional ◽

Hydrogen Oxidation ◽

Bayesian Optimization ◽

High Entropy Alloy ◽

Onset Potential ◽

High Entropy ◽

Co Oxidation Reaction

In recent years, the development of complex multi-metallic nanomaterials like high entropy alloy (HEA) catalysts has gained popularity. Composed of 5 or more metals, the compositions of HEAs exhibit extreme diversity. This is both a promising avenue to identify new catalysts and a severe constraint on their preparation and study. To address the challenges related to the preparation, study and optimization of HEAs, machine learning solutions are attractive. In this paper, the composition of PtRuPdRhAu hydrogen oxidation catalysts is optimized for the CO oxidation reaction. This is achieved by constructing a dataset using Bayesian optimization as guidance. For this quinary nanomaterial, the best performing composition was found within the first 35 experiments. However, the dataset was expanded until a total of 68 samples were investigated. This final dataset was used to construct a random forest regression model and a linear model. These machine learned models were used to assess the relationships between the concentrations of the consituent elements and the CO oxidation reaction onset potential. The onset potentials were found to correlate with the composition dependent adsorption energy of *OH obtained from density functional theory. This study demonstrates, how machine learning can be employed in an experimental setting to investigate the vast compositional space of HEAs.

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A Density Functional Theory Study of the Hydrogen Absorption in High Entropy Alloy TiZrHfMoNb

Inorganic Chemistry ◽

10.1021/acs.inorgchem.0c00989 ◽

2020 ◽

Vol 59 (14) ◽

pp. 9774-9782 ◽

Cited By ~ 1

Author(s):

Jutao Hu ◽

Jinjing Zhang ◽

Haiyan Xiao ◽

Lei Xie ◽

Huahai Shen ◽

...

Keyword(s):

Density Functional Theory ◽

Hydrogen Absorption ◽

Density Functional ◽

High Entropy Alloy ◽

Density Functional Theory Study ◽

Functional Theory ◽

High Entropy

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Defect States Due to Silicon Dangling Bonds at the Si(100)/SiO2 Interface and the Passivation by Hydrogen Atoms

MRS Proceedings ◽

10.1557/proc-592-39 ◽

1999 ◽

Vol 592 ◽

Author(s):

C. Kaneta ◽

T. Yamasaki ◽

T. Uchiyama ◽

T. Uda ◽

K. Terakura

Keyword(s):

Band Gap ◽

Density Functional ◽

Interface States ◽

The Other ◽

Dangling Bond ◽

Dangling Bonds ◽

Defect States ◽

Hydrogen Atoms ◽

The Density Functional Theory ◽

Upper Level

ABSTRACTThe defect states due to the Si dangling-bonds at the Si(100)/SiO2 interface is investigated by employing the first-principles method based on the density functional theory. Two prototypes of the defects at the interface are considered. One exists on one end of a Si-Si dimer. On the other hand, the other exists on an edge of a Si-O-Si bridge. The electronic structures for these systems were calculated to investigate the interface states. For the former, two defect states strongly localizing on the silicon dangling bond at the interface appear in the band gap. The latter defect also generates two defect states. But the upper level is in the conduction band, while the lower level is in the band gap. It is also shown that the interface states completely disappear by introducing a H atom into the interface and terminating the dangling bonds. Our results suggest the silicon dangling-bond on a Si-Si dimer with no adjacent O atoms as a candidate for the Pb1 center.

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SIMULATION OF NANOSCALE ETCHING FOR NANOTUBE AND GRAPHENE DEVICES

MRS Proceedings ◽

10.1557/opl.2012.850 ◽

2012 ◽

Vol 1451 ◽

pp. 21-24

Author(s):

Koichi Kusakabe

Keyword(s):

Hydrogen Atom ◽

Density Functional ◽

Carbon Materials ◽

Tube Wall ◽

Hydrogen Atoms ◽

Functional Theory ◽

Wales Defect ◽

The Density Functional Theory ◽

Graphene Devices ◽

Tungsten Tip

ABSTRACTIn order to find an efficient method to etch nano-carbon materials by hydrogenation in a controlled manner, we have studied hydrogen-atom adsorption on various deformed nanotubes using computer simulations based on the density-functional theory. The nanotube with an atomic lack is compared to a deformed tube with the Stone-Wales defect and a twisted tube wall. Similar to the known experimental etching condition for graphene, an atomic lack is effective to accumulate hydrogen atoms around the defect. Compared to the flat graphene, however, nanotube walls with curvature allow on-top adsorption of a hydrogen atom and selectivity in the hydrogenated site becomes worse. To achieve a controlled etching process, usage of a tungsten tip which realizes focused hydrogenation is proposed for natotubes and curved graphene.

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Simultaneously enhancing the ultimate strength and ductility of high-entropy alloys via short-range ordering

Nature Communications ◽

10.1038/s41467-021-25264-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Shuai Chen ◽

Zachary H. Aitken ◽

Subrahmanyam Pattamatta ◽

Zhaoxuan Wu ◽

Zhi Gen Yu ◽

...

Keyword(s):

Mechanical Properties ◽

Ultimate Strength ◽

Short Range ◽

Density Functional ◽

High Entropy Alloy ◽

High Entropy ◽

Body Center Cubic ◽

Short Range Ordering ◽

Composite Microstructure ◽

Strength And Ductility

AbstractSimultaneously enhancing strength and ductility of metals and alloys has been a tremendous challenge. Here, we investigate a CoCuFeNiPd high-entropy alloy (HEA), using a combination of Monte Carlo method, molecular dynamic simulation, and density-functional theory calculation. Our results show that this HEA is energetically favorable to undergo short-range ordering (SRO), and the SRO leads to a pseudo-composite microstructure, which surprisingly enhances both the ultimate strength and ductility. The SRO-induced composite microstructure consists of three categories of clusters: face-center-cubic-preferred (FCCP) clusters, indifferent clusters, and body-center-cubic-preferred (BCCP) clusters, with the indifferent clusters playing the role of the matrix, the FCCP clusters serving as hard fillers to enhance the strength, while the BCCP clusters acting as soft fillers to increase the ductility. Our work highlights the importance of SRO in influencing the mechanical properties of HEAs and presents a fascinating route for designing HEAs to achieve superior mechanical properties.

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Dynamics of the structural transformation of crystalline hydrogen upon the transition into the conductive state under compression

Доклады Академии наук ◽

10.31857/s0869-56524856676-681 ◽

2019 ◽

Vol 485 (6) ◽

pp. 676-681

Author(s):

G. E. Norman ◽

I. M. Saitov

Keyword(s):

Electrical Conductivity ◽

Structural Transformation ◽

Density Functional ◽

Pair Correlation ◽

Solid Hydrogen ◽

Unit Cell ◽

Hydrogen Atoms ◽

Hydrogen Molecules ◽

The Density Functional Theory ◽

Conductive State

The structural transformation of solid hydrogen under compression along the isotherm of 100 K in the region of transition into the conductive state was studied within the density functional theory. The pressure, the pair correlation function of protons, the density of electron states, and the electrical conductivity were calculated within a range of hydrogen densities from 1,14 to 2,11 g/cm3. The transition of the monoclinic structure of molecular solid hydrogen into the orthorhombic Cmca structure with 12 hydrogen atoms in a unit cell was revealed. In this case, the electrical conductivity was observed to grow, though hydrogen remained molecular. Hydrogen molecules decomposed under compression to the density of 1,563 g/cm3. A unit cell, the thus-formed quasi-tetrahedron, was built of five protons with a distance of 0,92 Å from the central proton to the four others.

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Атомная и электронная структура реконструкций поверхности (111) в кристаллах ZnSe и CdSe

Физика твердого тела ◽

10.21883/ftt.2018.01.45308.136 ◽

2018 ◽

Vol 60 (1) ◽

pp. 187

Author(s):

В.Л. Бекенев ◽

С.М. Зубкова

Keyword(s):

First Principles ◽

Density Functional ◽

Hydrogen Atoms ◽

Functional Theory ◽

The Density Functional Theory ◽

A Charge ◽

Quantum Espresso ◽

First Time ◽

Vacuum Gap ◽

The Ideal

AbstractThe atomic and electron structure of four variants of polar (111)-(2 × 2) surfaces in ZnSe and CdSe terminated by a cation, namely, the ideal, relaxed, reconstructed, and relaxed after reconstruction surfaces, are calculated for the first time from the first principles. The surface is simulated by a film with a thickness of 12 atomic layers and a vacuum gap of ~16 Å in the layered superlattice approximation. Four fictitious hydrogen atoms with a charge of 0.5 electrons each are added for closing dangling Se bonds on the opposite side of the film. Ab initio calculations are performed using the QUANTUM ESPRESSO software based on the density functional theory. It is shown that relaxation results in splitting of atomic layers. We calculate and analyze the band structures and total and layer-wise densities of electron states for four variants of the surface.

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Nobel Metal Based High Entropy Alloy for Conversion of Carbon Dioxide (CO2) to Hydrocarbon

10.26434/chemrxiv.9777218.v1 ◽

2019 ◽

Author(s):

Subramanian Nellaiappan ◽

Nirmal Kumar ◽

Ritesh Kumar ◽

Arko Parui ◽

Kirtiman Deo Malviya ◽

...

Keyword(s):

First Principles ◽

Density Functional ◽

Noble Metals ◽

High Entropy Alloy ◽

Functional Theory ◽

Faradaic Efficiency ◽

High Entropy ◽

Gaseous Products ◽

Gaseous Hydrocarbons ◽

Carbon Dioxide Co2

Conversion of carbon-di-oxide into selective hydrocarbon using stable catalyst remains a holy-grail in catalysis community. The high overpotential, stability, and selectivity in use of a single metal-based catalyst still remain a challenge. In current work, instead of using pure noble metals (Ag, Au, and Pt) as the catalyst, a novel nanocrystalline high entropy alloy (HEA: AuAgPtPdCu) has been used for conversion of CO2 into gaseous hydrocarbons. Utilizing an approach of multi-metallic HEA, a Faradaic efficiency of about 100% towards gaseous products is obtained. The reason behind the superior catalytic activity of high entropy alloy (HEA) was established through first-principles based density functional theory (DFT) by comparing it with pristine Cu (111) surface. This is attributed to the reversal in adsorption trends for two out of the total eight intermediates - *OCH3 and *O on Cu(111) and HEA surfaces.

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