Excited states of tetrahedral single-core<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mrow><mml:mn>29</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>nanoparticles

Rao, Satish; Sutin, Jason; Clegg, Robert M.; Gratton, Enrico; Nayfeh, Munir H.; Habbal, Shadia Rifai; Tsolakidis, Argyrios; Martin, Richard M.

doi:10.1103/physrevb.69.205319

Cited by 45 publications

(48 citation statements)

References 36 publications

(60 reference statements)

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“…For these and other systems, there is great interest in charge-transfer excitations [35,36,37,38,39,40], but (as we later discuss) intermolecular charge transfer is a demanding problem for TDDFT. Another major area of application is clusters, large and small, covalent and metallic, and everything inbetween [41,42,43,44,45,46,47], including Met-Cars [48]. Several studies include solvation, for example, the behavior of metal ions in explicit water [49].…”

mentioning

confidence: 99%

Time-dependent density functional theory: Past, present, and future

Burke

Werschnik

Gross

2005

The Journal of Chemical Physics

851

586

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Time-dependent density functional theory (TDDFT) is presently enjoying enormous popularity in quantum chemistry, as a useful tool for extracting electronic excited state energies. This article discusses how TDDFT is much broader in scope, and yields predictions for many more properties. We discuss some of the challenges involved in making accurate predictions for these properties.Kohn-Sham density functional theory [1,2,3] is the method of choice to calculate ground-state properties of large molecules, because it replaces the interacting manyelectron problem with an effective single-particle problem that can be solved much faster. Time-dependent density functional theory (TDDFT) applies the same philosophy to time-dependent problems. We replace the complicated many-body time-dependent Schrödinger equation by a set of time-dependent single-particle equations whose orbitals yield the same time-dependent density n(r, t). We can do this because the Runge-Gross theorem [4] proves that, for a given initial wavefunction, particle statistics and interaction, a given time-dependent density n(r, t) can arise from at most one time-dependent external potential v ext (r, t). We define time-dependent Kohn-Sham (TDKS) equations that describe N non-interacting electrons that evolve in v S (r, t), but produce the same n(r, t) as that of the interacting system of interest. Development and applications of TDDFT have enjoyed exponential growth in the last few years [5,6,7,8], and we hope this merry trend will continue.The scheme yields predictions for a huge variety of phenomena, that can largely be classified into three groups: (i) the non-perturbative regime, with systems in laser fields so intense that perturbation theory fails, (ii) the linear (and higher-order) regime, which yields the usual optical response and electronic transitions, and (iii) back to the ground-state, where the fluctuation-dissipation theorem produces ground-state approximations from TDDFT treatments of excitations.In the first, non-perturbative regime, we have systems in intense laser fields with electric field strengths that are comparable to or even exceed the attractive Coulomb field of the nuclei [5]. The time-dependent field cannot be treated perturbatively, and even solving the time-dependent Schrödinger equation for the evolution of two interacting electrons is barely feasible with present-day computer technology [9]. For more electrons in a time-dependent field, wavefunction methods are prohibitive, and in the regime of (not too high) laser intensities, where the electron-electron interaction is still of importance TDDFT is essentially the only practical scheme available. With the recent advent of atto-second laser pulses, the electronic time-scale has become accessible. Theoretical tools to analyze the dynamics of excitation processes on the attosecond time scale will become more and more important. An example of such a tool is the time-dependent electron localization function (TDELF) [10,11]. This quantity allows the time-resolved observation of ...

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mentioning

confidence: 99%

Time-dependent density functional theory: Past, present, and future

Burke

Werschnik

Gross

2005

The Journal of Chemical Physics

851

586

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“…The particles are produced by dispersion of (100) oriented, 1 -10 ohm-cm resistivity, ptype boron doped Si, by lateral anodization in hydrogen peroxide and HF acid [15][16][17][18][19][20][21][22]26 . Subsequent immersion in an ultra-sound acetone or water bath dislodges the ultrasmall particles.…”

Section: Methodsmentioning

confidence: 99%

Observation of linear solid-solid phase transformation in silicon nanoparticles

et al. 2012

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In bulk single crystal silicon, the semiconducting diamond to metallic ß-Sn phase transformation nucleates on defects, and is manifested by a sharp uptake in light absorption at a threshold of ~ 11 Gpa, accompanied with the creation of nanosized (20-50 nm) fragmentation domains. We report on the observation of linear uptakes in the absorption and in the luminescence, and with insignificant spectral change in ultrasmall 1 nm Si particles. We associate the gradual absorption uptake and luminescence yield with silicon-metal transformation on the surface. The insignificant change in the spectral content of the luminescence points to surface stability for particles, which are smaller than the bulk fragmentation domain. First-principle atomistic calculations yield absorption behavior that exhibits gradual uptake followed by sharp uptake at ~ 9-11 Gpa. The results point to the conclusion that two dimensional surface-like phase transformations are manifested by linear uptake in absorption and luminescence. a) m-nayfeh@illinois.edu 2

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“…The particles exhibit interesting optical properties such as luminescence in the visible part of the spectrum , second harmonic generation and laser oscillation . Under UV excitation, the Si1 particle generates blue spontaneous emission with a measured band-gap of 3 eV and the Si2.8 particle generates red emission with a 2 eV band-gap (Rao et al, 2004). Figure S1A (see Supplementary mate rials) shows the spontaneous emission of the two kinds of silicon particles.…”

Section: Methodsmentioning

confidence: 99%

“…This etching technique can be used to prepare 1-nanometer particles (Si1) and 2.8-nanometer particles (Si2.8), depending on etching conditions. Monte Carlo simulation of the Si1 particle suggests a filled fullerene structure of Si 29 H 24 , in which a central core silicon atom and four other silicon atoms are arranged in a tetrahedral coordination and the 24 remaining silicon atoms undergo a H-terminated bulk-like (2 × 1) reconstruction of dimer pairs on (0 0 1) facets (6 reconstructed surface dimers) (Rao et al, 2004). The particles exhibit interesting optical properties such as luminescence in the visible part of the spectrum , second harmonic generation and laser oscillation .…”

Section: Methodsmentioning

confidence: 99%