scholarly journals Ab Initio Study of the Combined Effects of Alloying Elements and H on Grain Boundary Cohesion in Ferritic Steels

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 291 ◽  
Author(s):  
Aparna P. A. Subramanyam ◽  
Abril Azócar Guzmán ◽  
Smobin Vincent ◽  
Alexander Hartmaier ◽  
Rebecca Janisch
Keyword(s):  
Grain Boundary ◽  
Density Functional ◽  
Detrimental Effect ◽  
Density Functional Theory Calculations ◽  
Alloying Elements ◽  
Ferritic Steels ◽  
Functional Theory ◽  
Substitutional Element ◽  
Spin Polarized ◽  
Interstitial Elements

Hydrogen enhanced decohesion is expected to play a major role in ferritic steels, especially at grain boundaries. Here, we address the effects of some common alloying elements C, V, Cr, and Mn on the H segregation behaviour and the decohesion mechanism at a Σ 5 ( 310 ) [ 001 ] 36.9 ∘ grain boundary in bcc Fe using spin polarized density functional theory calculations. We find that V, Cr, and Mn enhance grain boundary cohesion. Furthermore, all elements have an influence on the segregation energies of the interstitial elements as well as on these elements’ impact on grain boundary cohesion. V slightly promotes segregation of the cohesion enhancing element C. However, none of the elements increase the cohesion enhancing effect of C and reduce the detrimental effect of H on interfacial cohesion at the same time. At an interface which is co-segregated with C, H, and a substitutional element, C and H show only weak interaction, and the highest work of separation is obtained when the substitute is Mn.

scholarly journals Pd/Pt embedded CN monolayers as efficient catalysts for CO oxidation

2019 ◽  
Vol 21 (46) ◽  
pp. 25743-25748
Author(s):  
Yong-Chao Rao ◽  
Xiang-Mei Duan
Keyword(s):  
Density Functional Theory ◽  
Co Oxidation ◽  
Density Functional ◽  
Carbon Nitride ◽  
Density Functional Theory Calculations ◽  
Catalytic Performance ◽  
Functional Theory ◽  
Spin Polarized ◽  
Planar Carbon

The catalytic performance of Pd/Pt embedded planar carbon nitride for CO oxidation has been investigated via spin-polarized density functional theory calculations.

scholarly journals Breathing distortions in the metallic, antiferromagnetic phase of LaNiO$_3$

2018 ◽  
Vol 5 (3) ◽  
Author(s):  
Alaska Subedi
Keyword(s):  
Density Functional ◽  
Recent Observation ◽  
Quantum Critical Point ◽  
Three Dimensional ◽  
Density Functional Theory Calculations ◽  
Antiferromagnetic Phase ◽  
Functional Theory ◽  
Antiferromagnetic Ordering ◽  
Spin Polarized ◽  
Structural Fluctuations

I study the structural and magnetic instabilities in LaNiO_33 using density functional theory calculations. From the non-spin-polarized structural relaxations, I find that several structures with different Glazer tilts lie close in energy. The PnmaPnma structure is marginally favored compared to the R\overline{3}cR3¯c structure in my calculations, suggesting the presence of finite-temperature structural fluctuations and a possible proximity to a structural quantum critical point. In the spin-polarized relaxations, both structures exhibit the \uparrow\!\!0\!\!\downarrow\!\!0↑0↓0 antiferromagnetic ordering with a rock-salt arrangement of the octahedral breathing distortions. The energy gain due to the breathing distortions is larger than that due to the antiferromagnetic ordering. These phases are semimetallic with small three-dimensional Fermi pockets, which is largely consistent with the recent observation of the coexistence of antiferromagnetism and metallicity in LaNiO_33 single crystals by Guo et al. [Nat. Commun. 9, 43 (2018)].

Density functional theory calculations of atomic, electronic and thermodynamic properties of cubic LaCoO3and La1−xSrxCoO3surfaces

RSC Advances ◽  
2015 ◽  
Vol 5 (1) ◽  
pp. 760-769 ◽  
Author(s):  
Shuguang Zhang ◽  
Ning Han ◽  
Xiaoyao Tan
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Phase Diagrams ◽  
Thermodynamic Stability ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Spin Polarized

Spin-polarized DFT calculations were used to investigate the atomic, electronic structures of LaCoO3and La1−xSrxCoO3surfaces. The thermodynamic stability of these surfaces was analyzed with phase diagrams. Influence of Sr-doping was also examined.

Two dimensional MoS2 meets porphyrins via intercalation to enhance the electrocatalytic activity toward hydrogen evolution

Nanoscale ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 3780-3785 ◽  
Author(s):  
Ik Seon Kwon ◽  
In Hye Kwak ◽  
Hafiz Ghulam Abbas ◽  
Hee Won Seo ◽  
Jaemin Seo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Electrocatalytic Activity ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Two Dimensional ◽  
Functional Theory ◽  
Spin Polarized

Mn-Porphyrin-MoS2 exhibits excellent electrocatalytic activity toward the hydrogen evolution reaction, which is supported by spin-polarized density functional theory calculations.

Intercalation of cobaltocene into WS2 nanosheets for enhanced catalytic hydrogen evolution reaction

2019 ◽  
Vol 7 (14) ◽  
pp. 8101-8106 ◽  
Author(s):  
In Hye Kwak ◽  
Hafiz Ghulam Abbas ◽  
Ik Seon Kwon ◽  
Yun Chang Park ◽  
Jaemin Seo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Spin Polarized ◽  
Catalytic Hydrogen ◽  
Catalytic Hydrogen Evolution ◽  
Ws2 Nanosheets

Cobaltocene-intercalated WS2 nanosheets exhibit excellent catalytic activity toward the hydrogen evolution reaction, which is supported by spin-polarized density functional theory calculations.

scholarly journals A DFT investigation of the mechanisms of CO2 and CO methanation on Fe (111)

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Caroline R. Kwawu ◽  
Albert Aniagyei ◽  
Richard Tia ◽  
Evans Adei
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Environmentally Benign ◽  
Methane Formation ◽  
Functional Theory ◽  
Co Methanation ◽  
Detailed Mechanism ◽  
Catalytic Surfaces ◽  
Methanol Formation ◽  
Spin Polarized

AbstractInsight into the detailed mechanism of the Sabatier reaction on iron is essential for the design of cheap, environmentally benign, efficient and selective catalytic surfaces for CO2 reduction. Earlier attempts to unravel the mechanism of CO2 reduction on pure metals including inexpensive metals focused on Ni and Cu; however, the detailed mechanism of CO2 reduction on iron is not yet known. We have, thus, explored with spin-polarized density functional theory calculations the relative stabilities of intermediates and kinetic barriers associated with methanation of CO2 via the CO and non-CO pathways on the Fe (111) surface. Through the non-CO (formate) pathway, a dihydride CO2 species (H2CO2), which decomposes to aldehyde (CHO), is further hydrogenated into methoxy, methanol and then methane. Through the CO pathway, it is observed that the CO species formed from dihydroxycarbene is not favorably decomposed into carbide (both thermodynamically and kinetically challenging) but CO undergoes associative hydrogenation to form CH2OH which decomposes into CH2, leading to methane formation. Our results show that the transformation of CO2 to methane proceeds via the CO pathway, since the barriers leading to alkoxy transformation into methane are high via the non-CO pathway. Methanol formation is more favored via the non-CO pathway. Iron (111) shows selectivity towards CO methanation over CO2 methanation due to differences in the rate-determining steps, i.e., 91.6 kJ mol−1 and 146.2 kJ mol−1, respectively.

Hydrogen passivation of vacancies in diamond: Electronic structure and stability from ab initio calculations

MRS Advances ◽  
2017 ◽  
Vol 2 (5) ◽  
pp. 309-314 ◽  
Author(s):  
Kamil Czelej ◽  
Piotr Śpiewak
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Electron Conductivity ◽  
Synthesis Methods ◽  
Hydrogen Passivation ◽  
Functional Theory ◽  
Subsequent Formation ◽  
Hydrogen Incorporation ◽  
Spin Polarized ◽  
Hybrid Density Functional

ABSTRACTPoint defects in diamond such as vacancies act as a strong donor compensation center; therefore, remarkably reduce electron conductivity of diamond-based devices. Artificial synthesis methods of n-type diamond utilize the hydrogen-containing precursors enabling its diffusion into diamond crystal and subsequent formation of hydrogen-vacancy complexes. Here we employ spin-polarized, hybrid density functional theory calculations, in order to characterize the electronic properties and stability of hydrogen-passivated vacancies in diamond. We found strong thermodynamic preference for hydrogen passivation of four vacancy-related dangling bonds. An analysis of formation energy vs Fermi level diagrams indicate, that strong donor compensation effect associated with vacancies can be entirely neutralized by hydrogen incorporation. Thus, a careful control of hydrogen partial pressure in the growth process might be crucial to improve the electron conductivity of n-type diamond.

scholarly journals CO2 activation and dissociation on the low miller index surfaces of pure and Ni-coated iron metal: a DFT study

2017 ◽  
Vol 19 (29) ◽  
pp. 19478-19486 ◽  
Author(s):  
Caroline R. Kwawu ◽  
Richard Tia ◽  
Evans Adei ◽  
Nelson Y. Dzade ◽  
C. Richard A. Catlow ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Dft Study ◽  
Co2 Activation ◽  
Mechanistic Studies ◽  
Functional Theory ◽  
Miller Index ◽  
Iron Metal ◽  
Spin Polarized

We have used spin polarized density functional theory calculations to perform extensive mechanistic studies of CO2 dissociation into CO and O on the clean Fe(100), (110) and (111) surfaces and on the same surfaces coated by a monolayer of nickel.

scholarly journals A DFT+U investigation of hydrogen adsorption on the LaFeO3(010) surface

2017 ◽  
Vol 19 (10) ◽  
pp. 7399-7409 ◽  
Author(s):  
Isaac W. Boateng ◽  
Richard Tia ◽  
Evans Adei ◽  
Nelson Y. Dzade ◽  
C. Richard A. Catlow ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Adsorption Mechanism ◽  
Hydrogen Adsorption ◽  
Density Functional Theory Calculations ◽  
Nickel Metal ◽  
Functional Theory ◽  
Nickel Metal Hydride ◽  
Lanthanum Ferrite ◽  
Spin Polarized

Lanthanum ferrite (LaFeO3) is a technologically important electrode material for nickel–metal hydride batteries, energy storage and catalysis. In the present study, we have employed spin-polarized density functional theory calculations, with the Hubbard U correction (DFT+U), to unravel the adsorption mechanism of H2 on the LaFeO3(010) surface.

scholarly journals Insights into the Electrochemical Behavior of Mercury on Graphene/SiC Electrodes

2019 ◽  
Vol 5 (3) ◽  
pp. 51 ◽  
Author(s):  
Shtepliuk ◽  
Vagin ◽  
Yakimova
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Detrimental Effect ◽  
Deep Understanding ◽  
Density Functional Theory Calculations ◽  
Toxic Element ◽  
Functional Theory ◽  
Oxidation Reduction ◽  
Sensing Platforms ◽  
Shed Light

Fast and real time detection of Mercury (Hg) in aqueous solutions is a great challenge due to its bio-accumulative character and the detrimental effect on human health of this toxic element. Therefore, development of reliable sensing platforms is highly desirable. Current research is aiming at deep understanding of the electrochemical response of epitaxial graphene to Mercury exposure. By performing cyclic voltammetry and chronoamperometry measurements as well as density functional theory calculations, we elucidate the nature of Hg-involved oxidation-reduction reactions at the graphene electrode and shed light on the early stages of Hg electrodeposition. The obtained critical information of Hg behavior will be helpful for the design and processing of novel graphene-based sensors.

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