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 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)].

scholarly journals Native Defects and their Doping Response in the Lithium Solid Electrolyte Li7La3Zr2O12

2019 ◽  
Author(s):  
Alex Squires ◽  
David Scanlon ◽  
Benjamin Morgan
Keyword(s):  
Density Functional ◽  
Ionic Conductivities ◽  
Density Functional Theory Calculations ◽  
Defect Chemistry ◽  
Functional Theory ◽  
Native Defects ◽  
Synthesis Conditions ◽  
Reducing Conditions ◽  
Solid State Batteries ◽  
Hybrid Density Functional

<p>The Li-stuffed garnets Li<sub><i>x</i></sub>M<sub>2</sub>M<sub>3</sub>′O<sub>12</sub> are promising Li-ion solid electrolytes with potential use in solid-state batteries. One strategy for optimising ionic conductivities in these materials is to tune lithium stoichiometries through aliovalent doping, which is often assumed to produce proportionate numbers of charge compensating Li vacancies. The native defect chemistry of the Li-stuffed garnets, and their response to doping, however, are not well understood, and it is unknown to what degree a simple vacancy-compensation model is valid. Here, we report hybrid density-functional–theory calculations of a broad range of native defects in the prototypical Li-garnet Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub>. We calculate equilibrium defect concentrations as a function of synthesis conditions, and model the response of these defect populations to extrinsic doping. We predict a rich defect chemistry that includes Li and O vacancies and interstitials, and significant numbers of cation-antisite defects. Under reducing conditions, O vacancies act as colour-centres by trapping electrons. We find that supervalent (donor) doping does not produce charge compensating Li vacancies under all synthesis conditions; under Li-rich / Zr-poor conditions the dominant compensating defects are Li<sub>Zr</sub> antisites, and Li stoichiometries strongly deviate from those predicted by simple “vacancy compensation” models.<br></p>

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.

Optoelectronic and solar cell applications of Janus monolayers and their van der Waals heterostructures

2019 ◽  
Vol 21 (34) ◽  
pp. 18612-18621 ◽  
Author(s):  
M. Idrees ◽  
H. U. Din ◽  
R. Ali ◽  
G. Rehman ◽  
T. Hussain ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Solar Cell ◽  
Density Functional ◽  
Van Der Waals ◽  
Density Functional Theory Calculations ◽  
Hybrid Density Functional Theory ◽  
Van Der Waals Heterostructures ◽  
Functional Theory ◽  
Hybrid Density Functional

Janus monolayers and their van der Waals heterostuctures are investigated by hybrid 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.

scholarly journals A theoretical investigation on the isomerism and the NMR properties of thiosemicarbazones

2007 ◽  
Vol 5 (2) ◽  
pp. 396-419 ◽  
Author(s):  
N. Nuwan De Silva ◽  
Titus Albu
Keyword(s):  
Density Functional ◽  
Chemical Shifts ◽  
Intermolecular Hydrogen Bond ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
1H And 13C Nmr ◽  
Nmr Characterization ◽  
Hybrid Density Functional ◽  
Nmr Properties

AbstractHybrid density functional theory calculations at the mPW1PW91/6-31+G(d,p) level of theory have been used to investigate the optimized structures and other molecular properties of five different series of thiosemicarbazones. The investigated compounds were obtained from acenaphthenequinone, isatin and its derivatives, and alloxan. The focus of the study is the isomerism and the NMR characterization of these thiosemicarbazones. It was found that only one isomer is expected for thiosemicarbazones and methylthiosemicarbazones, while for dimethylthiosemicarbazones, two isomers are possible. All investigated thiosemicarbazones exhibit a hydrazinic proton that is highly deshielded and resonates far downfield in the proton NMR spectra. This proton is a part of a characteristic sixmembered ring, and its NMR properties are a result of its strong, intermolecular hydrogen bond. The relationships between the calculated 1H and 13C NMR chemical shifts and various geometric parameters are reported.

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