Vanadium pentoxide (V2O5): a van der Waals density functional study

The past few years has brought renewed focus on the physics behind the class of materials characterized by long-range interactions and wide regions of low electron density, sparse matter. There is now much work on developing the appropriate algorithms and codes able to correctly describe this class of materials within a parameter-free quantum physical description. In particular, van der Waals (vdW) forces play a major role in building up material cohesion in sparse matter. This work presents an application to the vanadium pentoxide (V2O5) bulk structure of two versions of the vdW-DF method, a first-principles procedure for the inclusion of vdW interactions in the context of density functional theory (DFT). In addition to showing improvement compared to traditional semilocal calculations of DFT, we discuss the choice of various exchange functionals and point out issues that may arise when treating systems with large amounts of vacuum.Comment: 5 pages, 4 figures, 1 tabl

JRC data for the Ti-48 standard

A measurement of the 48Ti(n,n’gamma)48Ti reaction was performed at the GELINA neutron source of EC-JRC-IRMM using the GAINS spectrometer with the purpose of establishing a new gamma-ray standard for neutron induced cross section measurements. A natural target was used and the gamma-production cross section was measured for 10 transitions in the neutron energy range 0-18 MeV. The lowest achieved uncertainty was 4.8%.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

First Results of the 140^{140}Ce(n,γ)141^{141}Ce Cross-Section Measurement at n_TOF

An accurate measurement of the $^{140}$Ce(n,γ) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the $^{140}$Ce capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in $^{140}$Ce to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the $^{140}$Ce Maxwellian-averaged cross-section

First Results of the 140^{140}Ce(n,γ)141^{141}Ce Cross-Section Measurement at n_TOF

An accurate measurement of the $^{140}$Ce(n,γ) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the $^{140}$Ce capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in $^{140}$Ce to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the $^{140}$Ce Maxwellian-averaged cross-section

Measurement of the angular distribution of neutrons scattered from deuterium below 3 MeV

The differential cross section of neutron scattering on deuterium was investigated in the energy range from 400 keV to 2.5 MeV using the recoil detection method, irradiating with monoenergetic neutrons a proportional counter filled with deuterated gases. Comparing simulations of the transport of neutrons and recoil nuclei in the detector to the experimental pulse-height distribution, it was possible to establish a procedure for the determination of the coefficients of the Legendre expansion of the n-d angular distribution

Measurement of the angular distribution of neutrons scattered from deuterium below 3 MeV

The differential cross section of neutron scattering on deuterium was investigated in the energy range from 400 keV to 2.5 MeV using the recoil detection method, irradiating with monoenergetic neutrons a proportional counter filled with deuterated gases. Comparing simulations of the transport of neutrons and recoil nuclei in the detector to the experimental pulse-height distribution, it was possible to establish a procedure for the determination of the coefficients of the Legendre expansion of the n-d angular distribution.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Measurement of the differential cross section of neutron scattering on deuterium in the neutron energy range from 400 keV to 2.5 MeV

The angular distribution of n-d scattering was investigated in the energy range from 400 keV to 2.5 MeV using the recoil detection method, irradiating a proportional counter filled with deuterated gases with monoenergetic neutrons. Several techniques were employed to minimise the contribution of photons to the pulse-height distributions. A dedicated Monte Carlo model was developed to determine the differential cross section that best reproduces the measurements. The results are compared with theoretical calculation and the ENDF/B-VII.1 evaluation.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

[Copper(I)(Pyridine-Containing Ligand)] Catalyzed Regio- and Steroselective Synthesis of 2‑Vinylcyclopropa[<i>b</i>]indolines from 2‑Vinylindoles

A [copper­(I)­pyridine-containing ligand]-catalyzed reaction between 2-vinylindoles and diazo esters is described. The reaction allows for the synthesis of a series of 2-vinylcyclopropa­[<i>b</i>]­indolines with excellent levels of regio- and sterocontrol under mild conditions