arXiv subjects

J. G. Tobin

Publications and source records attributed to J. G. Tobin.

4 recordsLinked to original sources

arXiv2024

A Reassessment of 5f Occupation in Plutonium

A detailed spectroscopic simulation of the original Pu N4,5 and O4,5 X-Ray Absorption Spectroscopy (XAS) has been performed. Additionally, a fundamental flaw in the Electron Energy Loss Spectroscopy (EELS) measurement has been corrected. Thus, the determination of the 5f occupation (n) in elemental Pu has been re-evaluated with the result that n = 5.0 +/- 0.1 for alphaPu and n = 4.9 +/- 0.2 for deltaPu. These values are significantly lower than the value of ~5.5 that was propagated earlier.

cond-mat.mtrl-sci↗

arXiv2021

The relativistic 5f electronic structure of delocalized $α$-U and localized $δ$-Pu from the self consistent vertex corrected GW approach and X-ray Emission Spectroscopy

The recently developed self-consistent vertex corrected GW method is used to calculate the 5f electronic structure in delocalized $α$-U and localized $δ$-Pu, each of which is confirmed by the historical experimental approaches of direct and inverse photoemission. Tender X-Ray Emission Spectroscopy (XES), in a novel application to 5f electronic structure, is used to experimentally prove the existence of 5f delocalization in $α$-U.

cond-mat.mtrl-sci↗

arXiv2016

Probing 5f-state configurations in URu2Si2 with U L3-edge resonant x-ray emission spectroscopy

Resonant x-ray emission spectroscopy (RXES) was employed at the U L3 absorption edge and the La1 emission line to explore the 5f occupancy, nf, and the degree of 5f orbital delocalization in the hidden order compound URu2Si2. By comparing to suitable reference materials such as UF4, UCd11, and alpha-U, we conclude that the 5f orbital in URu2Si2 is at least partially delocalized with nf = 2.87 +/- 0.08, and does not change with temperature down to 10 K within the estimated error. These results place further constraints on theoretical explanations of the hidden order, especially those requiring a localized f2 ground state.

cond-mat.str-el↗

arXiv2015

Pressure-Induced Structural Phase Transition in CeNi: X-ray and Neutron Scattering Studies and First-Principles Calculations

The pressure-induced structural phase transition in the intermediate-valence compound CeNi has been investigated by X-ray and neutron powder diffraction techniques. For the first time it is shown that the structure of the pressure-induced CeNi phase (phases) can be described in terms of the Pnma space group. Equations of state for CeNi on both sides of the phase transition are derived and an approximate P-T phase diagram is suggested for P < 8 GPa and T < 300 K. The observed Cmcm -> Pnma structural transition is analyzed using density functional theory (DFT) calculations, which successfully reproduce the ground state volume, the phase transition pressure, and the volume collapse associated with the phase transition.

cond-mat.str-el↗