Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Effects of sample size and statistical weights on fluctuations in the c12(c12, alpha)ne20 reactions,

Abstract: Absolute values of the differential cross sections for the reaction ${\mathrm{C}}^{12}({\mathrm{C}}^{12}, \ensuremath{\alpha}){\mathrm{Ne}}^{20}$ to the ground and 1.63-MeV states are given at 100-keV energy intervals between 20.3- and 25.6-MeV bombarding energy at eight equally spaced angles between 3 and 73\ifmmode^\circ\else\textdegree\fi{} in the laboratory, as well as some more detailed angular distributions at selected energies. Both differential cross sections and angle-integrated data are shown to fluctuate strongly with energy. A quantitative comparison between the properties of the fluctuations and the predictions of the statistical theory of the compound nucleus (used in the spirit of Ericson) is presented. The effects of making observations on a sample of finite size are illustrated in detail and are shown in some cases to lead to results that are readily mistaken for evidence of direct interaction. Fluctuations of cross sections involving sums of several incoherent components of different weights are calculated and compared with experiment and with the usual estimates based on equal weights. The proper weight coefficients for the calculation are derived from the treatment of the average cross sections in an accompanying paper. Agreement is found in all cases between observations and the statistical compound-nucleus picture although the finite-sample effects allow a contribution to the cross sections from direct reactions of 30% or less.

Spin ordering and electronic texture in the bilayer iridate Sr 3 Ir 2 O 7

Abstract: Through a neutron scattering, charge transport, and magnetization study, the correlated ground state in the bilayer iridium oxide Sr${}_{3}$Ir${}_{2}$O${}_{7}$ is explored. Our combined results resolve scattering consistent with a high temperature magnetic phase that persists above 600 K, reorients at the previously defined ${T}_{\text{AF}}=280$ K, and coexists with an electronic ground state whose phase behavior suggests the formation of a fluctuating charge or orbital phase that freezes below ${T}^{*}\ensuremath{\approx}70$ K. Our study provides a window into the emergence of multiple electronic order parameters near the boundary of the metal to insulator phase transition of the $5d$ ${J}_{\text{eff}}=1/2$ Mott phase.

An experimental and computational study of CO2 adsorption in the sodalite-type M-BTT (M = Cr, Mn, Fe, Cu) metal–organic frameworks featuring open metal sites

Abstract: We present a comprehensive investigation of the CO2 adsorption properties of an isostructural series of metal-organic frameworks, M-BTT (M = Cr, Mn, Fe, Cu; BTT3- = 1,3,5-benzenetristetrazolate), which exhibit a high density of open metal sites capable of polarizing and binding guest molecules. Coupling gas adsorption measurements with in situ neutron and X-ray diffraction experiments provides molecular-level insight into the adsorption process and enables rationalization of the observed adsorption isotherms. In particular, structural data confirms that the high initial isosteric heats of CO2 adsorption for the series are directly correlated with the presence of open metal sites and further reveals the positions and orientations of as many as three additional adsorption sites. Density functional theory calculations that include van der Waals dispersion corrections quantitatively support the observed structural features associated with the primary and secondary CO2 binding sites, including CO2 positions and orientations, as well as the experimentally determined isosteric heats of CO2 adsorption.

Short-range magnetic interactions in the spin-ice compound Ho 2 Ti 2 O 7

Abstract: Magnetization and susceptibility studies on single crystals of the pyrochlore Ho{sub 2}Ti{sub 2}O{sub 7} are reported. Magnetization isotherms are shown to be qualitatively similar to that predicted by the nearest-neighbor spin-ice model. Below the lock-in temperature, T{sup *}{approx_equal}1.97 K, magnetization is consistent with the locking of spins along [111] directions in a specific two-spins-in, two-spins-out arrangement. Below T{sup *} the magnetization for B||[111] displays a two step behavior signaling the breaking of the ice rules.