Solution to the Modified Helmholtz Equation for Arbitrary Periodic Charge Densities

Winkelmann, Miriam; Blügel, Stefan; Napoli, Edoardo Di; Wortmann, Daniel

doi:10.3389/fphy.2020.618142

Cited by 4 publications

(4 citation statements)

References 16 publications

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“…As we are primarily interested in core electronic states, a full-potential method is required. This work primarily uses the full-potential linearized augmented plane wave (FLAPW) method − as implemented in the open-source FLEUR code. , …”

Section: Methodsmentioning

confidence: 99%

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Interpretation of Oxygen 1s X-ray Photoelectron Spectroscopy of ZnO

2023

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X-ray photoelectron spectroscopy (XPS) is widely used to determine the chemical and electronic states of atoms within a material. However, it is often complex to interpret the O 1s region in metal oxides, where an ∼531 eV binding energy feature appears between lattice oxygen (∼530 eV) and oxygen-containing surface species (∼532 eV). This feature has been vaguely ascribed to oxygen vacancies or oxygen deficient regions for many decades. This work employs full-potential density functional theory to calculate the binding energies of the O 1s electrons under two-and threedimensional periodic boundary conditions as a probe of expected XPS spectra. ZnO is used as an example system. Both bulk crystal regions containing a range of oxygen defects and slabs with a range of surface terminations and functionalizations have been considered. The slabs considered are mostly {1010} and {1120} surfaces that are not expected to be reconstructed from the cleaved bulk structure. The resulting O 1s binding energies show no signature for oxygen defects in bulk regions. Furthermore, the 531 eV binding energy feature often ascribed to oxygen vacancies or oxygen deficient regions can instead be readily explained by the O 1s electrons from water molecules strongly bound to the exposed ZnO surface (i.e., chemisorbed, as distinct from more loosely bound water) or surface oxygen passivated with hydrogen. This work will rectify many misinterpretations of XPS data of the O 1s region in metal oxides, provide guidance for precisely understanding the oxygen states of a material, and subsequently enable the real origin of material properties to be revealed.

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Section: Methodsmentioning

confidence: 99%

“…This work primarily uses the full-potential linearized augmented plane wave (FLAPW) method 30−32 as implemented in the open-source FLEUR code. 33,34 All calculations were performed using the PBE functional. 35 Most computational parameters were left at the FLEUR defaults.…”

Section: Methodsmentioning

confidence: 99%

Interpretation of Oxygen 1s X-ray Photoelectron Spectroscopy of ZnO

2023

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“…The relation between density and can be established by using a modified Helmholtz 39 like equation that is a static version of Eq. (3) of Ref.…”

Section: Hydrodynamic Matrix and Daf From Generalized Hydrodynamic Modelmentioning

confidence: 99%

Auto-correlations of microscopic density fluctuations for Yukawa fluids in the generalized hydrodynamics framework with viscoelastic effects

Dhaka

Subhash

Bandyopadhyay

et al. 2022

Sci Rep

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The present work develops a theoretical procedure for obtaining transport coefficients of Yukawa systems from density fluctuations. The dynamics of Yukawa systems are described in the framework of the generalized hydrodynamic (GH) model that incorporates strong coupling and visco-elastic memory effects by using an exponentially decaying memory function in time. A hydrodynamic matrix for such a system is exactly derived and then used to obtain an analytic expression for the density autocorrelation function (DAF)—a marker of the time dynamics of density fluctuations. The present approach is validated against a DAF obtained from numerical data of Molecular Dynamics (MD) simulations of a dusty plasma system that is a practical example of a Yukawa system. The MD results and analytic expressions derived from the model equations are then used to obtain various transport coefficients and the latter are compared with values available in the literature from other models. The influence of strong coupling and visco-elastic effects on the transport parameters are discussed. Finally, the utility of our calculations for obtaining reliable estimates of transport coefficients from experimentally determined DAF is pointed out.

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“…Detailed derivations of the pseudo-charge method for the screened Poisson equation are provided in [27,41,42], and appendix A.…”

Section: Preconditioners: Kerker and Restamentioning

confidence: 99%

Resta-like preconditioning for self-consistent field iterations in the linearized augmented planewave method

Kim

May

2022

Electron. Struct.

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Convergence in self-consistent-field cycles can be a major computational bottleneck of density-functional theory calculations. We propose a Resta-like preconditioning method for full-potential all-electron calculations in the linearized augmented planewave (LAPW) method to smoothly converge to self-consistency. We implemented this preconditioner in the exciting code and apply it to the two semiconducting systems of MoS2 slabs and P-rich GaP(100) surfaces as well as the metallic system Au(111), containing a sufficiently large amount of vacuum. Two magnetic systems of 19-atoms Fe and Co are also considered. Our calculations demonstrate that the implemented scheme performs reliably as well as more efficiently regardless of system size, suppressing long-range charge sloshing. While the suitability of this preconditioning higher for semiconducting systems, the convergence for metals is, depending on the system, only slightly de- or increased and thus still trustworthy to apply. Furthermore, a mixing algorithm with the preconditioner shows an improvement over that with the Kerker preconditioner for the investigated semiconducting systems.

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Solution to the Modified Helmholtz Equation for Arbitrary Periodic Charge Densities

Cited by 4 publications

References 16 publications

Interpretation of Oxygen 1s X-ray Photoelectron Spectroscopy of ZnO

Interpretation of Oxygen 1s X-ray Photoelectron Spectroscopy of ZnO

Auto-correlations of microscopic density fluctuations for Yukawa fluids in the generalized hydrodynamics framework with viscoelastic effects

Resta-like preconditioning for self-consistent field iterations in the linearized augmented planewave method

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