Band-Structure Contributions to X-Ray Emission and Absorption Spectra and Edges in Magnesium

Gupta, R. S.; Freeman, Arthur J

doi:10.1103/physrevlett.36.1194

Cited by 88 publications

(16 citation statements)

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“…(E b ), Ref [12]. (vIP, d ) and Ref [13]. (s-and p-components of DOS at Fermi energy).Cluster size E b (eV) −∆ 2 E (eV) Eg (eV) vIP (eV) aIP (eV) vDE (eV)Fig.…”

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confidence: 96%

Metallic evolution of small magnesium clusters

Akola

Rytkönen

Manninen

2001

The European Physical Journal D

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Structural and electronic properties of small magnesium clusters (N ≤ 13) are studied using a first-principles simulation method in conjunction with the density functional theory and generalized gradient correction approximation for the exchange-correlation energy functional. It is observed that the onset of metallization of magnesium clusters is hard to assign since both the s-p hybridization and the energy gap between the valence and conduction bands do not evolve rapidly towards the known bulk properties. Instead these quantities show a slow and nonmonotonic evolution.PACS. 36.40.Cg Electronic and magnetic properties of clusters -36.40.Mr Spectroscopy and geometrical structure of clusters -71.24.+q Electronic structure of clusters and nanoparticles

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“…(E b ), Ref [12]. (vIP, d ) and Ref [13]. (s-and p-components of DOS at Fermi energy).Cluster size E b (eV) −∆ 2 E (eV) Eg (eV) vIP (eV) aIP (eV) vDE (eV)Fig.…”

mentioning

confidence: 96%

Metallic evolution of small magnesium clusters

Akola

Rytkönen

Manninen

2001

The European Physical Journal D

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“…15 are in very good agreement with those calculated by other workers. 16,17 The unoccupied TDOS, with a linear background and Fermi-function cutoff at T = 150 K, is represented by the solid line. The filled part of the TDOS is shown dashed.…”

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confidence: 99%

Unoccupied-Band Narrowing in Na and its Effect on the X-Ray-AbsorptionKEdge

et al. 1988

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The first Na AT-edge absorption measurements are reported. The data reveal a narrowing of the unfilled density of states analogous to that observed in a recent photoemission study of the conduction band and in very good agreement with new band-structure calculations. The narrowing is found to be essential for obtaining compatibility among the A-edge threshold exponent, the Z,2,3-edge exponent, and the singularity index in core-level photoemission. PACS numbers: 78.70.Dm, 71.25.Pi, 71.45.GmThe nearly free-electron-like behavior of monovalent alkali metals has historically made them ideal systems for testing solid-state theory and experiment.* From the earliest calculations of cohesive energies in metals 2 to investigations of many-body phenomena in x-ray edge spectroscopy, 3 these systems continue to provide important new insight. The most recent example is an angleresolved photoemission study of Na, 4 which indicated an occupied bandwidth considerably narrower than that predicted by one-electron theory even with inclusion of self-energy corrections. 5,6 This disparity subsequently led to several new theoretical treatments of these corrections. 7 " 10 It is because Na is the most free-electron-like of all the alkali metals, 11 and thus yields the most easily interpretable photoemission spectrum, that the need for such fundamental improvements in band-structure theory became so apparent.In this Letter we report the first x-ray-absorption measurements from the K edge of Na. The data reflect the one-electron transition density of unoccupied p states and the many-body effects of the \s core hole on the threshold edge shape. 12 " 14 Specific predictions regarding both these features, based on band-structure calculations and other independent measurements, were made several years ago 15 but have remained untested because of the experimentally inconvenient energy of the Na K edge. Our new absorption measurements show, just as in the case of the Na photoemission, that significant discrepancies exist between experiment and conventional theory. If, however, the recently discovered narrowing of the occupied band in Na (Ref. 4) is extended to the unoccupied part as well, excellent agreement between the theoretical description of the edge and experiment is obtained. Through study of this model system, the present work provides independent support for the new corrections to the Na band structure without invoking surface effects 10 and reaffirms the validity of the many-body theory of threshold excitations. 12,13 Implications of band narrowing on the interpretation of edge results from other metals are also discussed.The Na data were obtained on the JUMBO beam line at the Stanford Synchrotron Radiation Laboratory. Asymmetrically cut double monochromating beryl (lOTO) crystals (2*/ = 15.95 A) were used to excite the Na K edge at 1071 eV. The samples were prepared by repeated evaporations onto 150-K substrates in a base pressure of -10~1 0 Ton*. Surface contamination, checked by Auger electron and absorption spectroscopies, was fo...

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“…Transitions from the outermost p shells of Rb and Cs yield line shapes similar to the L II,III edge shapes of Na, Mg, and Al, 25,26 but the spectra of rare-gas impurities in alkali-metal hosts mysteriously exhibit ramp thresholds, 39 and the soft x-ray lineshapes of binary alloys [13][14][15]20,25,26,37 such as Li 1−x Mg x sometimes have threshold behaviors quite different from the edge shapes of their metallic components. Gupta et al [80][81][82] have shown that by taking band-structure effects into account in the one-electron theory, one obtains spectra with the qualitative features observed in the spectra of Na and Mg. Thus band-structure effects may be important for understanding edge shapes, even in free-electron metals.…”

Section: Introductionmentioning

confidence: 99%

“…͑1.3͒; [80][81][82]88 ͑ii͒ exchange mixing of spin-orbit split edges is perhaps significant; 76,95 ͑iii͒ many-electron effects omitted from the ND model conceivably distort the edge shapes; 84,103 and ͑iv͒ exact solutions of the ND model perhaps disagree with the asymptotic solution Eq. ͑1.3͒, for energies a significant distance from threshold.…”

Section: Introductionmentioning

confidence: 99%

X-ray line shapes of metals: Exact solutions of a final-state interaction model

Swarts¹,

Dow²

2005

Phys. Rev. B

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By means of model calculations for an independent-electron metal, we obtain exact line shapes for the photon absorption, emission, and photoemission spectra of core states, including electronic relaxation. In all cases we find an x-ray edge anomaly. For the absorption and emission spectra this anomaly is superposed on a continuum resembling Elliott exciton theory. We display how the spectra evolve from the exciton limit to the free-electron limit as the final-state interaction strength is decreased or the Fermi energy increased. We compare the spectra obtained for different final-state interactions and find that different types of interactions produce different spectral shapes. Away from threshold the absorption and emission profiles show an enhancement of the free-electron result, as predicted by the screened-exciton theory. Our results offer potential explanations for ͑i͒ incompatibilities between threshold exponents and exponents extracted from other data, ͑ii͒ the occurrence of nearly symmetric x-ray photoemission lines, and ͑iii͒ the lack of mirror symmetry of absorption and emission edges.

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Band-Structure Contributions to X-Ray Emission and Absorption Spectra and Edges in Magnesium

Cited by 88 publications

References 8 publications

Metallic evolution of small magnesium clusters

Metallic evolution of small magnesium clusters

Unoccupied-Band Narrowing in Na and its Effect on the X-Ray-AbsorptionKEdge

X-ray line shapes of metals: Exact solutions of a final-state interaction model

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