Search results for "neutron"
showing 10 items of 2330 documents
Construction and characterization of models of hypercrosslinked polystyrene
2012
A simple algorithm involving classical molecular dynamics (MD) simulations is here suggested to build up models of hypercrosslinked polystyrene showing macroporous structure. The algorithm is composed by three consecutive stages: MD simulation of a single polystyrene coil, crosslink formation, and finally relaxation of the structure. The models, which are differentiated by the crosslinker concentration in the initial polystyrene chain, can be characterized by employing tools of the small angle neutron scattering analysis and procedures associated to the crosslinking algorithm, which allows one to discriminate among the different kinds of crosslinks between phenyl rings and to calculate the …
Collective features of Cr and Fe isotopes
2014
The question of the sudden increase of collectivity in neutron-rich nuclei when approaching N = 40 has recently interested both experimentalists and theorists. In this paper we study the development of collectivity along the chromium and iron isotopic chains. The calculations are performed within two different perspectives, namely, the proton-neutron interacting boson model (IBM-2) and interacting shell model (ISM) and compared with the available experimental data. The onset of collectivity is studied through nuclear quantities and observables that suggest differences in the nuclear structure of Cr and Fe isotopical chains. Furthermore, a prediction for the shape transition from a spherical…
Probing Sizes and Shapes of Nobelium Isotopes by Laser Spectroscopy
2018
Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on unique access to the differential mean-square charge radii of ^{252,253,254}No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton densi…
Influence of irradiation on the switching behavior in PZT thin films
2005
Spatially nonuniform imprint behavior induced by X-ray synchrotron, electron and neutron irradiation has been investigated in sol–gel Pb(Zr,Ti)O3 thin films. The analysis of the switching current data reveals the strong influence of irradiation on the switching current shape. The obtained effects have been explained as a result of acceleration of the bulk screening process induced by irradiation. It was shown that the spatial distribution of the internal bias field is determined by the domain structure existing during irradiation. The changes in the structural characteristics during fatigue cycling have been reveled by high resolution synchrotron X-ray diffraction experiments on (1 1 1)-ori…
Neutron Diffraction Study of the in Situ Oxidation of UO2
2009
This paper discusses uranium oxide crystal structure modifications that are observed during the low-temperature oxidation which transforms UO(2) into U(3)O(8). The symmetries and the structural parameters of UO(2), beta-U(4)O(9), beta-U(3)O(7), and U(3)O(8) were determined by refining neutron diffraction patterns on pure single-phase samples. Neutron diffraction patterns were also collected during the in situ oxidation of powder samples at 483 K. The lattice parameters and relative ratios of the four pure phases were measured during the progression of the isothermal oxidation. The transformation of UO(2) into U(3)O(8) involves a complex modification of the oxygen sublattice and the onset of…
ChemInform Abstract: Neutron Diffraction Study of the in situ Oxidation of UO2.
2009
This paper discusses uranium oxide crystal structure modifications that are observed during the low-temperature oxidation which transforms UO2 into U3O8. The symmetries and the structural parameters of UO2, β-U4O9, β-U3O7, and U3O8 were determined by refining neutron diffraction patterns on pure single-phase samples. Neutron diffraction patterns were also collected during the in situ oxidation of powder samples at 483 K. The lattice parameters and relative ratios of the four pure phases were measured during the progression of the isothermal oxidation. The transformation of UO2 into U3O8 involves a complex modification of the oxygen sublattice and the onset of complex superstructures for U4O…
Structure of Urea Clusters Confined in AOT Reversed Micelles
2003
The structure of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and that of urea containing AOT reversed micelles has been investigated by small-angle neutron scattering (SANS) and Fourier transform infrared (FT-IR) spectroscopy at different AOT concentrations and urea/AOT molar ratios. For the AOT/n-heptane system, SANS data analysis indicates that AOT molecules form prolate ellipsoidal aggregates, which grow asymmetrically along the major axis upon increasing the surfactant concentration. For the urea/AOT/n-heptane system, the SANS results are consistent with the hypothesis that urea is encapsulated as small-sized ellipsoidal hydrogen-bonded clusters within the hydrophilic micellar core of …
Small angle neutron scattering study of the quaternary structure of haemocyanin of Rapana thomasiana
1996
Abstract Small angle neutron scattering (SANS) experiments were performed on a series of solutions of haemocyanin (Hc) of Rapana thomasiana . In a first series of solutions, by changing the external contrast a model of the molecule that is apparently in disagreement with electron microscopy (EM) measurements was obtained. The apparent disagreement was resolved by performing experiments on a series of variable protein concentration solutions in D 2 O. The physical parameters of the model, extrapolated to zero concentration, are in excellent agreement with the EM results obtained on samples more dilute than those examined with SANS.
Two stage magnetic ordering and spin idle behavior of the coordination polymer Co3(OH)2(C4O4)2·3H2O determined using neutron diffraction.
2011
We report the magnetic structure of two of the magnetically ordered phases of Co(3)(OH)(2)(C(4)O(4))(2)·3H(2)O, a coordination polymer that consists of a triangular framework decorated with anisotropic Co(II) ions. The combination of neutron diffraction experiments and magnetic susceptibility data allows us to identify one phase as displaying spin idle behavior, where only a fraction of the moments order at intermediate temperatures, while at the lowest temperatures the system orders fully. This novel magnetic behavior is discussed within the framework of a simple Hamiltonian and representational analysis and rationalizes this multiphase behavior by considering the combination of frustratio…
Magnetic Polyoxometalates: Anisotropic Antiferro- and Ferromagnetic Exchange Interactions in the Pentameric Cobalt(II) Cluster [Co3W(D2O)2(CoW9O34)2…
2001
The ground-state properties of the pentameric Co(II) cluster [Co(3)W(D(2)O)(2)(CoW(9)O(34))(2)](12-) were investigated by combining magnetic susceptibility and low-temperature magnetization measurements with a detailed inelastic neutron scattering (INS) study on a fully deuterated polycrystalline sample of Na(12)[Co(3)W(D(2)O)(2)(CoW(9)O(34))(2)].46D(2)O. The encapsulated magnetic Co(5) unit consists of three octahedral and two tetrahedral oxo-coordinated Co(II) ions. Thus, two different types of exchange interactions are present within this cluster: a ferromagnetic interaction between the octahedral Co(II) ions and an antiferromagnetic interaction between the octahedral and the tetrahedral…