Magnetic susceptibility and the Faraday effect in orthorhombic DyAlO
3
single crystals were studied along the crystallographic
b
-axis, the axis of easy magnetization, in a temperature range 78–300 ...K. The Faraday rotation was measured on the basis of the temperature and spectral dependencies of the rotation angles θ of the major axis of the ellipse of light radiation polarization in a wavelength range 440–750 nm. At a wavelength of 506 nm, the dependence of the Verdet constant
V
on the magnetic susceptibility χ
M
was observed to be linear in a temperature range 85–300 K, and the paramagnetic Verdet constant
C
p
was calculated. A comparative analysis of the constants
C
p
and the effective frequencies ω
0
of allowed transitions in cubic
R
3
Al
5
O
12
garnets and
R
AlO
3
(
R
= Tb
3+
, Dy
3+
) orthoaluminate crystals was carried out in terms of the local site symmetry for rare-earth ions. The possibility of practical magneto-optical applications of the DyAlO
3
crystals is briefly discussed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A quantitative assessment is presented of the dislocation density and relative fractions of edge and screw dislocations in reactor-steel samples 16Cr–15Ni–3Mo–1Ti subjected to preliminary cold ...deformation by rolling and subsequent fast neutron irradiation using neutron diffraction analysis. The Williamson–Hall modified method was used for calculations. It is shown that the fast neutron irradiation leads to a decrease in the density of dislocations that appeared after samples deformation. The applicability of neutron diffraction analysis to the examination of dislocation structure of deformed and irradiated materials is shown.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An approach to validating calculations of electromagnetic fields formed upon the interaction between a narrowly directed pulse of ionizing radiation and a medium, done on the basis of the model of ...linear current, is proposed. The forms of the magnetic components of the electromagnetic field are derived by summing the fields of free electrons created as a result of passage of 10-MeV gamma quanta through the air at a pressure of 10 atm.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Optical absorption and photoluminescence (PL) spectra in the TbF3 crystals have been studied within the visible spectral range at the temperature of 90 K. Measurements of luminescence excitation ...spectra (LES) were carried out at temperatures of 25 and 300 K using the synchrotron radiation source. By comparison of PL and absorption spectra related to the optical transitions between Stark sublevels of 5D4 and 7F6 multiplets of Tb3+ ion at T = 90 K we can draw a diagram of the optical transitions between Stark sublevels and define their energies and positions in combining in optical transitions multiplets. It has been found that effect of the external magnetic field, which is parallel to a axis of the orthorhombic crystal, results in reduction of initial splitting of 10.7 cm−1 of well resolved doublet line of 7F6 → 5D4 absorption band observed in π polarization near 20,675 cm−1 with linear-polarized light propagated parallel to c crystallographic axis. At the same time in another experimental geometry, in which the external magnetic field is perpendicular to the a-b plane of the TbF3 crystal, an absorption line at ~20,730 cm−1 has the Zeeman splitting, which increases with the increase of magnetic strength. Such non-trivial behavior of the Zeeman effect in the TbF3 crystal is explained by peculiar features of magnetization of non-Kramers rare earth ions in crystal surroundings with CS symmetry, which is typical for crystallographic structure of trifluoride.
•Diagram of 5D4. → 7F6 transitions between Stark sublevels is made•Onset of PL bands of forbidden 4f.→ 4f transitions 5D4 → 7F6 is observed•Magnetic field results in reduction of initial splitting of 7F6. → 5D4 line•If the field is perpendicular to the a-b plane the quasi doublet does not split.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In order to further search efficient 8circulene materials for OLED applications we have theoretically investigated the structure and electronic absorption spectra of functionalized ...tetrabenzo8circulenes with different substituents in the outer perimeter. These hydrocarbon materials complement the wide family of 8circulenes which earlier have been demonstrated to possess promising emissive and exciplex-forming properties suitable for organic light emitting diodes. The hydrocarbon tetrabenzo8circulenes show saddle shape of the molecular skeleton which can exist in two different conformations with different curvatures of the macrocycle. The aromaticity, electronic structure and orbital pattern are found to be principally different for these two isomers, where the global minimum isomer is weakly antiaromatic and electronically less stable comparing with the non-aromatic local minimum structure. The absorption spectra are also very different: the global minimum structure is more active in the long-wavelength region while the local minimum isomer shows absorption only at short wavelengths. Our computational findings suggest a new concept for optical tuning of curved 8circulenes through conformational isomerization and aromaticity control, thus through structural variations without changing the molecular composition. Based on this principle we have designed novel functionalized 8circulenes with promising fluorescence activity.
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•Two conformational isomers of tetrabenzo8circulene have been theoretically studied.•Global minimum isomer is weakly antiaromatic and electronically less stable.•Local minimum isomer shows absorption only at short wavelengths.•Novel functionalized 8circulenes with promising fluorescence activity have been designed.•The concept of conformational-dependent fluorescence is proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Microstructure, martensitic transformation and mechanical properties of an ultrafine-grained Ti44Ni47Nb9 shape memory alloy processed by equal channel angular pressing were investigated. The as-ECAP ...processed sample is characterized by an inhomogeneous and refined microstructure. In β-Nb phase-rich region, the grains of matrix are elongated with high density dislocations. In β-Nb phase-free region, the microstructure is partial recovery and characterized by near-equiaxed grains. The heterogeneous microstructure is attributed to presence of β-Nb phase. Martensitic transformation behavior of the as-ECAP processed sample is characterized by a single-stage transformation. The thermal cycling stability of transformation and the mechanical properties are considerably improved due to a strengthening effect resulting from refined grain size and high dislocation density.
•Microstructure of the as-ECAP processed TiNiNb alloy is inhomogeneous.•Transformation temperatures are lower than those of the initial material.•Transformation stability and mechanical properties can be considerably improved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A series of thia7circulenes and novel Se-, Te-, S/Te-, and Se/Te-substituted 8circulenes have been studied by calculations of nucleus-independent chemical shift indices and gauge including ...magnetically induced currents to interpret the impact of heteroatoms on the aromatic properties of these polyheterocyclic species. The calculations indicate that all the studied hetero7circulenes and hetero8circulenes consist of two concentric subsystems: an inner seven- or eight-membered core is antiaromatic because of the existence of a paratropic ring current, and an outer system of benzene and hetarene rings that exhibit aromatic behaviour due to the circulation of diatropic ring currents. Thus, most of the hetero7circulenes can be considered as slightly antiaromatic because of the slight domination of the paratropic ring currents over the diatropic ones, whereas hetero8circulenes represent aromatic species due to the prevailing contribution of the diatropic currents. The antiaromaticity gradually increases with more scattered arrangements of the thiophene and benzene rings in each series of di-, tri-, tetra-, and pentathia7circulenes because of the reduced conjugation effect between the neighboring thiophene and benzene rings. Loss of planarity with increased strain leads to an increased antiaromatic character of the lower representatives of the thia
n
circulenes, whereas higher thia
n
circulenes demonstrate a more pronounced aromatic nature because of the small deviation from planarity. The ring current topology is found to be quite insensitive to the heteroatom type, number of hetarene rings and the size of the inner ring; this clearly manifests the special electronic structure of hetero
n
circulenes containing two concentric cyclic subsystems.
Computations reveal the structural and energetic aspects of aromaticity in heterocirculenes.
Since the advent of the first computers, chemists have been at the forefront of using computers to understand and solve complex chemical problems. As the hardware and software have evolved, so have ...the theoretical and computational chemistry methods and algorithms. Parallel computers clearly changed the common computing paradigm in the late 1970s and 80s, and the field has again seen a paradigm shift with the advent of graphical processing units. This review explores the challenges and some of the solutions in transforming software from the terascale to the petascale and now to the upcoming exascale computers. While discussing the field in general, NWChem and its redesign, NWChemEx, will be highlighted as one of the early codesign projects to take advantage of massively parallel computers and emerging software standards to enable large scientific challenges to be tackled.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
In accordance with the priority directions of development of the motor transport complex of the RF, the use of NGV fuel in transport should expand and by 2035 reach 50% of the total number ...of trucks and buses in large cities. This is due to a number of factors. The paper presents the results of studies confirming the effectiveness of using natural gas to reduce soot emissions with exhaust gases. In particular, the dynamics of the formation and burnout of soot particles by the angle of rotation of the crankshaft at the working operating mode is considered.
Fluorescent materials are widely used for anti-counterfeiting of information security and commodities. However, the increasing requirements for fluorescent anti-counterfeiting technology urgently ...require the development of novel fluorescent materials with multicolor fluorescence, single component, and excellent stability. Herein, a color tunable Ba0·94Ca0.06ScO2F: Eu2+, Bi3+, K+ perovskite with dependence of excitation wavelength for high-level anti-counterfeiting is reported. The fluorescence spectra of Ba0·94Ca0.06ScO2F: Eu2+, Bi3+, K+ perovskite show the tunable emission band with the peak between 479 and 509 nm. It is worth noting that the peak intensity ratio at 479 and 509 nm changes with the dependence of the excitation wavelength. Meanwhile, the snowflake pattern is designed to demonstrate the potential applications in anti-counterfeiting, which obviously shows four different color patterns under the sunlight, 320 360, and 415 nm excitation, respectively.
•A novel Eu and Bi codoped (Ba,Ca)ScO2F perovskite with dual emission was proposed.•Color tunable (Ba,Ca)ScO2F:Eu2+, Bi3+, K+ perovskite with dependence of excitation wavelength was discovered.•Energy re-absorption process from Eu2+ to Bi3+ ions in Ba0·94Ca0.06ScO2F:Eu2+, Bi3+, K+ was revealed.•(Ba,Ca)ScO2F:Eu2+, Bi3+, K+ perovskite is an advanced material for fluorescent anti-counterfeiting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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