Taming convergence in the determinant approach for x-ray excitation spectra

Liang, Yufeng

doi:10.1103/physrevb.100.075121

Cited by 18 publications

(15 citation statements)

References 68 publications

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“…In that context there has been some discussion of "many-electron" effects on oscillator strengths for x-ray transitions. 389,390 What "many-electron" means in this context is multi-determinant character in the final state, which is of course included automatically in a LR-TDDFT calculation.…”

Section: Transition Potential Methodsmentioning

confidence: 99%

Density Functional Theory for Electronic Excited States

Herbert¹

2022

Preprint

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This chapter provides a basic introduction to excited-state extensions of density functional theory (DFT), including time-dependent (TD-)DFT in both its linear-response and its explicitly time-dependent formulations. As applied to the Kohn-Sham DFT ground state, linear-response theory affords an eigenvaluetype problem for the excitation energies in a basis of singly-excited Slater determinants, and is widely known simply as "TDDFT" despite its frequency-domain formulation. This form of TDDFT is the mostly widely-used quantum-chemical method for excited states, due to a favorable combination of low cost and reasonable accuracy. The chapter surveys the accuracy of linear-response TDDFT, which is generally more sensitive to the details of the exchange-correlation functional as compared to ground-state DFT, and also describes some known systemic problems exhibited by this approach. Some of those problems can be corrected on a case-by-case basis using orbital-optimized, excited-state self-consistent field (SCF) calculations, in what is known as excited-state Kohn-Sham theory or a "∆SCF" procedure, a class of methods that includes restricted open-shell Kohn-Sham theory. Recent successes of these approaches are highlighted, including double excitations and core-level excitations. Finally, explicitly time-dependent (or "real-time") TDDFT involves propagation of the molecular orbitals in time following an external perturbation, according to the Kohn-Sham analogue of the time-dependent Schrödinger equation. The time-dependent approach has been used to model strong-field electron dynamics, and in the weak-field limit it provides a route to broadband spectra based on the time evolution of the dipole moment function. This is useful for describing high-energy excitations (as in x-ray spectroscopy) and in systems where the density of states is high, as demonstrated by a few examples.

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Section: Transition Potential Methodsmentioning

confidence: 99%

Density Functional Theory for Electronic Excited States

Herbert¹

2022

Preprint

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“…Similar effects exist for skyrmions, but few studies have considered the influence of disorder on the AFM skyrmion dynamics. In principle, the Magnus force can help an FM skyrmion to avoid individual impurities, while the straight motion of AFM skyrmions may experience more hindering effects from the pinning sites [55]. The issue may become more complicated in a granular film [56].…”

Section: (A)] Described By the Hamiltonianmentioning

confidence: 99%

Recent progress in antiferromagnetic dynamics

Yuan¹,

Yuan²,

Duine³

et al. 2021

EPL

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Spintronics, since its inception, has mainly focused on ferromagnetic materials for manipulating the spin degree of freedom in addition to the charge degree of freedom, whereas much less attention has been paid to antiferromagnetic materials. Thanks to the advances of micro-nano-fabrication techniques and the electrical control of the Néel order parameter, antiferromagnetic spintronics is booming as a result of abundant room temperature materials, robustness against external fields and dipolar coupling, and rapid dynamics in the terahertz regime. For the purpose of applications of antiferromagnets, it is essential to have a comprehensive understanding of the antiferromagnetic dynamics at the microscopic level. Here, we first review the general form of equations that govern both antiferromagnetic and ferrimagnetic dynamics. This general form unifies the previous theories in the literature. We also provide a survey for the recent progress related to antiferromagnetic dynamics, including the motion of antiferromagnetic domain walls and skyrmions, the spin pumping and quantum antiferromagnetic spintronics. In particular, open problems in several topics are outlined. Furthermore, we discuss the development of antiferromagnetic quantum magnonics and its potential integration with modern information science and technology.perspective

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“…Despite the recent emergence of many highly accurate first-principles approaches to simulate XPS and XAS signatures based on many-body perturbation theory [79,[119][120][121], approximate core-hole simulation methods remain essential workhorses for highly complex spectroscopy simulations with applications ranging from in-operando electrocatalysis [122] to ultrafast dynamics [123] and pump-probe spectroscopy [124]. The efficiency of these methods enables the creation of high-volume data [110,125,126] which can be used for machine-learning-assisted spectral assignment [127][128][129].…”

Section: Conclusion and Future Outlookmentioning

confidence: 99%

The Nuts and Bolts of Ab-Initio Core-Hole Simulations for K-shell X-Ray Photoemission and Absorption Spectra

Klein,

Hall,

Maurer

2020

Preprint

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X-ray photoemission (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy play an important role in investigating the structure and electronic structure of materials and surfaces. Ab-initio simulations provide crucial support for the interpretation of complex spectra containing overlapping signatures. Approximate core-hole simulation methods based on Density Functional Theory such as the Delta-Self-Consistent-Field (∆SCF) method or the transition potential (TP) method are widely used to predict K-shell XPS and NEXAFS signatures of organic molecules, inorganic materials and metal-organic interfaces at reliable accuracy and affordable computational cost. We present the numerical and technical details of our variants of the ∆SCF and transition potential method (coined ∆IP-TP) to simulate XPS and NEXAFS transitions. Using exemplary molecules in gas-phase, in bulk crystals, and at metal-organic interfaces, we systematically assess how practical simulation choices affect the stability and accuracy of simulations. These include the choice of exchange-correlation functional, basis set, the method of core-hole localization, and the use of periodic boundary conditions. We particularly focus on the choice of aperiodic or periodic description of systems and how spurious charge effects in periodic calculations affect the simulation outcomes. For the benefit of practitioners in the field, we discuss sensible default choices, limitations of the methods, and future prospects.

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Taming convergence in the determinant approach for x-ray excitation spectra

Cited by 18 publications

References 68 publications

Density Functional Theory for Electronic Excited States

Density Functional Theory for Electronic Excited States

Recent progress in antiferromagnetic dynamics

The Nuts and Bolts of Ab-Initio Core-Hole Simulations for K-shell X-Ray Photoemission and Absorption Spectra

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