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[en] Using first-principles calculations, we performed systematic investigation on the electronic and mechanical properties of sodium chlorides with different stoichiometries at high pressures. It was found that most of the phases are metallic except the Pnma-NaCl_3 with a gap of 2.155 eV. The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization. Accompanied by metallization, the Na_mCl_n crystals exhibit good ductility in contrast to the brittle NaCl crystal, due to the changes of binding features induced by high pressure. These results are expected to be useful for understanding the exotic properties of NaCl at high pressures. - Highlights: • We performed systematic investigation on the electronic and mechanical properties of Na_mCl_n. • The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization at high pressures. • The Na_mCl_n crystals exhibit good ductility in contrast to the brittle NaCl crystal. • The P4/mmm-Na_3Cl possesses the best ductility and the semiconducting Pnma-NaCl_3 has the largest hardness.
[en] Complete text of publication follows. The possible risk of an unexpected nuclear accident or violent terror attack necessitates different methods and processes potentially applicable in emergency. After the event fast and reliable dose assessments should be given so that arrangements and intervention could start as soon as possible. Retrospective dosimetry is one of the most important tool of accidental dosimetry for dose estimation when dose measurement was not planned and there is no dose data available as a result of a nuclear accident. Luminescent materials are suitable for retrospective dosimetry using TL and/or OSL analysis. Several materials have luminescence properties in the environment, but in the situation mentioned it is suggested to use not just natural substances, but also personal belongings carried by victims, who received the dose. In our environment many objects can be applied as natural dosimeters, having suitable thermoluminescent (TL) and optically stimulated luminescent (OSL) properties. The paper discusses the recent developments, the analysis of luminescence and the dose response curves of various electronic components and the common (table) salt (NaCl) using Daybreak TL reader for retrospective dosimetry purposes. Basic TL properties of these materials (e.g. fading and reproducibility) have also been investigated and will be shown in this study.
[en] The experiments were carried out on NaCl monocrystals, obtained by the Czochralsky method. The sintering was carried out in air, at the temperature order of 700-7500C, under different conditions: different position, different orientation and different space between crystals. In dependence on the position of the crystals that were sintered, we carried out two series of experiments. In the first series one crystal was on top of the other one, and in the second - one beside the other
[en] An ''ab initio'' self-consistent-field crysttalline-cluster approach to the study of deep impurity states in insulators is proposed. It is shown that, in spite of being a cluster calculation, the interaction of the impurity with the crystal environment is fully taken into account. It is also shown that the present representation of the impurity states is, at least, as precise as the crystalline cluster representation of the pure crystal electronic structure. The procedure has been tested by performing the calculation of the electronic structure of the U center in a sodium chloride crystal, and it has been observed that the calculated γ1 - γ15 absorption energy is in good agreement with experiment. (author)
[pt]Um procedimento autoconsistente de primeiros principios e proposto. Mostra-se que, apesar de ser um calculo de agregado, a interacao entre a impureza e o envoltorio cristalino foi corretamente levada em conta. Mostra-se tambem que a presente representacao dos estados de impureza e, pelo menos, tao precisa quanto a representacao do cristal puro pelo metodo de agregado cristalino. O metodo proposto foi testado calculando a estrutura eletronica do centro U em um cristal de NaCl. Observou-se que o valor teorico do pico de absorcao γ1 - γ15 esta em boa concordancia com a experiencia. (autor)
[en] In this paper we have determined the behaviour of the protection of the coating of mirrors, using the technique of Electrochemical Impedance Spectroscopy. The system is evaluated with the sodium chloride electrolyte (3% weight) for 0, 5, 24 h and 15 de having the electrolyte introduced in the measuring cell. The paint system used in the protection of mirrors behaves very much like the classical models proposed for the corrosion that a given coating system undergoes in an aggressive medium, according to the results obtained in Electrochemical Impedance Spectroscopy tests for different contact times contact of the system with the sodium chloride electrolyte at weight of 3%. (Author) 13 refs