Excited-state Forces within a First-principles Green's Function Formalism

We present a new first-principles formalism for calculating forces for optically excited electronic states using the interacting Green's function approach with the GW-Bethe Salpeter Equation method. This advance allows for efficient computation of gradients of the excited-state Born-Oppenheimer energy, allowing for the study of relaxation, molecular dynamics, and photoluminescence of excited states. The approach is tested on photoexcited carbon dioxide and ammonia molecules, and the calculations accurately describe the excitation energies and photoinduced structural deformations.Comment: 2 figures and 2 table

Coupling of Nonlocal Potentials to Electromagnetic Fields

Nonlocal Hamiltonians are used widely in first-principles quantum calculations; the nonlocality stems from eliminating undesired degrees of freedom, e.g. core electrons. To date, attempts to couple nonlocal systems to external electromagnetic (EM) fields have been heuristic or limited to weak or long wavelength fields. Using Feynman path integrals, we derive an exact, closed-form coupling of arbitrary EM fields to nonlocal systems. Our results justify and clarify the couplings used to date and are essential for systematic computation of linear and especially nonlinear response.Comment: 1 figure, 1 tabl

Bipolar rechargeable lithium battery for high power applications

Viewgraphs of a discussion on bipolar rechargeable lithium battery for high power applications are presented. Topics covered include cell chemistry, electrolytes, reaction mechanisms, cycling behavior, cycle life, and cell assembly

Diameter and Chirality Dependence of Exciton Properties in Carbon Nanotubes

We calculate the diameter and chirality dependences of the binding energies, sizes, and bright-dark splittings of excitons in semiconducting single-wall carbon nanotubes (SWNTs). Using results and insights from {\it ab initio} calculations, we employ a symmetry-based, variational method based on the effective-mass and envelope-function approximations using tight-binding wavefunctions. Binding energies and spatial extents show a leading dependence with diameter as $1/d$ and $d$, respectively, with chirality corrections providing a spread of roughly 20% with a strong family behavior. Bright-dark exciton splittings show a $1/d^2$ leading dependence. We provide analytical expressions for the binding energies, sizes, and splittings that should be useful to guide future experiments

Theory and it ab initio calculation of radiative lifetime of excitons in semiconducting carbon nanotubes

We present theoretical analysis and first-principles calculation of the radiative lifetime of excitons in semiconducting carbon nanotubes. An intrinsic lifetime of the order of 10 ps is computed for the lowest optically active bright excitons. The intrinsic lifetime is however a rapid increasing function of the exciton momentum. Moreover, the electronic structure of the nanotubes dictates the existence of dark excitons nearby in energy to each bright exciton. Both effects strongly influence measured lifetime. Assuming a thermal occupation of bright and dark exciton bands, we find an effective lifetime of the order of 10 ns at room temperature, in good accord with recent experiments.Comment: 12 pages, 3 figure

Excitonic Effects and Optical Spectra of Single-Walled Carbon Nanotubes

Many-electron effects often dramatically modify the properties of reduced dimensional systems. We report calculations, based on an many-electron Green's function approach, of electron-hole interaction effects on the optical spectra of small-diameter single-walled carbon nanotubes. Excitonic effects qualitatively alter the optical spectra of both semiconducting and metallic tubes. Excitons are bound by ~ 1 eV in the semiconducting (8,0) tube and by ~ 100 meV in the metallic (3,3) tube. These large many-electron effects explain the discrepancies between previous theories and experiments.Comment: 6 pages, 3 figures, 2 table

Selection Rules for One- and Two-Photon Absorption by Excitons in Carbon Nanotubes

Recent optical absorption/emission experiments showed that the lower energy optical transitions in carbon nanotubes are excitonic in nature, as predicted by theory. These experiments were based on the symmetry aspects of free electron-hole states and bound excitonic states. The present work shows, however, that group theory does not predict the selection rules needed to explain the two photon experiments. We obtain the symmetries and selection rules for the optical transitions of excitons in single-wall carbon nanotubes within the approach of the group of the wavevector, thus providing important information for the interpretation of theoretical and experimental optical spectra of these materials.Comment: 4 pages, 1 figure, 1 tabl

Pathological Staging of Renal Cell Carcinoma: A Review of 300 Consecutive Cases

Aims: Pathological staging of renal cell carcinoma (RCC) can be challenging compared to other cancer types, as invasion often manifests as finger‐like protrusions into vascular spaces or renal sinus tissue. Although prior studies have shown larger tumour size to be correlated highly with renal sinus invasion, prospective data on evaluating pathological stage are limited. We evaluated a large series reported by one urological pathologist. Methods and results: Three hundred consecutive specimens were reviewed. Tumours larger than 5 cm were routinely sampled extensively or grossly re‐reviewed when no extrarenal extension was identified on initial examination. Apparent multifocal disease was assessed critically for intravascular spread. Retrograde venous invasion was reported in 15 of 300 (5%) cases, 13 of 15 of which were clear cell RCC. Of a total of 163 specimens with clear cell histology, only five of 34 (15%) tumours 7 cm or larger were reported as pT2, all of which had an explanatory comment indicating the absence of definitive extrarenal spread. In contrast, 15 of 20 (75%) pT2 tumours were non‐clear cell histology (papillary, chromophobe and translocation‐associated). Comparing pT3a or higher tumours, the median tumour size in cases with retrograde venous invasion was 8.0 cm, compared to 6.2 cm in cases without retrograde venous invasion (P = 0.005). ConclusionsOur findings support that retrograde venous invasion should be considered carefully before diagnosing multifocal clear cell RCC, which is rare in the sporadic setting. In the absence of vascular invasion, multifocal clear cell papillary RCC can be a mimic. pT2 occurs more frequently with non‐clear cell histology (particularly papillary or chromophobe RCC).https://scholarlycommons.henryford.com/merf2019basicsci/1002/thumbnail.jp