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>

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><br></p> <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.</p>

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>

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>

Blue and black phosphorene on metal substrates: a density functional theory study

2021 ◽  
Author(s):  
Abhishek Kumar Adak ◽  
Devina Sharma ◽  
Shobhana Narasimhan
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Chemical Potential ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Atomic Size ◽  
Metal Substrates ◽  
Synthesis Conditions ◽  
Black Phosphorene ◽  
Blue Phosphorene

Abstract We have performed density functional theory calculations to study blue phosphorene and black phosphorene on metal substrates. The substrates considered are the (111) and (110) surfaces of Al, Cu, Ag, Ir, Pd, Pt and Au and the (0001) and (10$\bar{1}$0) surfaces of Zr and Sc. The formation energy $E_{\rm F}$ is negative (energetically favorable) for all 36 combinations of overlayer and substrate. By comparing values of $\Delta{\Omega}$, the change in free energy per unit area, as well as the overlayer-substrate binding energy $E_{\rm b}$, we identify that Ag(111), Al(110), Cu(111), Cu(110) and possibly Au(110) may be especially suitable substrates for the synthesis and subsequent exfoliation of blue phosphorene, and the Ag(110) and Al(111) substrates for the synthesis of black phosphorene. However, these conclusions are drawn assuming the source of P atoms is bulk phosphorus, and can alter upon changing synthesis conditions (chemical potential of phosphorus). Thus, when the source of phosphorus atoms is P$_4$, blue phosphorene is favored only over Pt(111). We find that for all combinations of overlayer and substrate, the charge transfer per bond can be captured by the universal descriptor $\mathcal{D} = \Delta \chi/\Delta \mathcal{R}$, where $\Delta \chi$ and $\Delta \mathcal{R}$ are, respectively, the differences in electronegativity and atomic size between phosphorus and the substrate metal.

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 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.

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.

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