0000000000485251
AUTHOR
Roberto González
Kinetics of nanocavity formation based onF-center aggregation in thermochemically reduced MgO single crystals
Division of Materials Science, Office of Basic Energy Sciences, SC 13, U.S. Department of Energy, Germantown, Maryland 20874-1290~Received 9 February 2001; published 19 July 2001!The dynamics of interacting F centers resulting in F aggregates and nanocavities is modeled in thermo-chemically reduced MgO single crystals. We have recently shown that thermal annealing of thermochemicallyreduced MgO with an exceptionally high F-center concentration (6310
Photoconversion and dynamic hole recycling process in anion vacancies in neutron-irradiated MgO crystals
Optical spectroscopy and theory demonstrate that photon excitation of the positively charged anion vacancies (F{sup +} centers) at 5.0 eV in neutron-irradiated MgO crystals releases holes that are subsequently trapped at {ital V}-type centers, which are cation vacancies charge compensated by impurities, such as Al{sup 3+}, F{sup {minus}}, and OH{sup {minus}} ions. The concentration of trapped-hole centers was found to exceed that of available anion vacancies. The disproportionately large amount of holes produced is attributed to a dynamic recycling process, by which the F{sup +} center serves to release a hole to the {ital V}-type centers and subsequently trap a hole from an Fe{sup 3+} ion.…
Individual and culture-level components of survey response styles: A multi-level analysis using cultural models of selfhood
Variations in acquiescence and extremity pose substantial threats to the validity of cross-cultural research that relies on survey methods. Individual and cultural correlates of response styles when using 2 contrasting types of response mode were investigated, drawing on data from 55 cultural groups across 33 nations. Using 7 dimensions of self-other relatedness that have often been confounded within the broader distinction between independence and interdependence, our analysis yields more specific understandings of both individual- and culture-level variations in response style. When using a Likert-scale response format, acquiescence is strongest among individuals seeing themselves as simi…
Photoconversion of F+ centers in neutron-irradiated MgO
Abstract In neutron-irradiated MgO crystals, experiments and theory demonstrate that photon excitation of the positively charged anion vacancies (F+ centers) at 5.0 eV releases holes that are subsequently trapped at V-type centers, which are cation vacancies charge-compensated by impurities, such as Al3+, F−, and OH− ions. A photoconversion mechanism occurs very likely via electron transfer to F+ centers from the quasi-local states which are induced in the valence band. INDO quantum chemical simulations of F+ centers confirmed the appearance of two induced quasi-local states located at 1.2 and 2.0 eV below the top of the valence band.
Dynamics of F-center annihilation in thermochemically reduced MgO single crystals
Optical absorption measurements were used to monitor the thermal annihilation of oxygen vacancies (F-centers) in thermochemically reduced MgO crystals. The annihilation characteristics were sample-dependent and varied strongly with the F-center concentration. Different mechanisms for the destruction of F centers are suggested depending on their concentration.
Diffusion-controlled annihilation and aggregation of F-centers in thermochemically reduced MgO crystals
Abstract The dynamics of F-center (an oxygen vacancy which has trapped two electrons) aggregation in thermochemically reduced MgO single crystals with an exceptionally high F-center concentration (6×1018 cm−3) is discussed. A theory of the Mg nanocavity formation process is developed based on diffusion-controlled aggregation of elastically interacting F centers and their annihilation at traps. We show that in contrast to the generally accepted viewpoint, the F centers in the bulk are not annealed out at the external sample surface but at internal defects, such as dislocations, subgrain boundaries and impurities. The mutual attraction of the F centers is a key factor controlling the aggregat…
Being oneself through time: Bases of self-continuity across 55 cultures
Çalışmada 60 yazar bulunmaktadır. Bu yazarlardan sadece Bursa Uludağ Üniversitesi mensuplarının girişleri yapılmıştır. Self-continuity - the sense that one's past, present, and future are meaningfully connected - is considered a defining feature of personal identity. However, bases of self-continuity may depend on cultural beliefs about personhood. In multilevel analyses of data from 7287 adults from 55 cultural groups in 33 nations, we tested a new tripartite theoretical model of bases of self-continuity. As expected, perceptions of stability, sense of narrative, and associative links to one's past each contributed to predicting the extent to which people derived a sense of self-continuity…
Ab initioand semiempirical calculations ofH−centers in MgO crystals
The atomic and electronic structure of ${\mathrm{H}}^{\ensuremath{-}}$ ions substituting for ${\mathrm{O}}^{2\ensuremath{-}}$ ions in regular sites in MgO crystals are calculated using an ab initio Hartree-Fock (HF) cluster approach and its semiempirical version, intermediate neglect of the differential overlap. The theoretical optical absorption energy is predicted to be 10 eV, which is supported by analysis of experimental data for the ${\mathrm{H}}^{\ensuremath{-}}$ centers in a series of ionic crystals. The HF simulations of ${\mathrm{H}}^{\ensuremath{-}}$ ion diffusion via direct interstitial hops along the [100] axis predict an activation energy of about 3 eV.