Ideal stoichiometric technetium nitrides under pressure: a first-principles study

Technetium nitrides with various ideal stoichiometries have been investigated with the first-principle method at the pressures between 0–60 GPa. It have been found that there could be many stable technetium nitrides including Tc₃N, Tc₂N, TcN, Tc₂N₃, TcN₂, TcN₃, and TcN₄, among which Tc₃N and Tc₂N sub-nitrides are synthesizable at zero pressure and could be applied to nuclear waste management, such as separate radioactive 99Tc from nuclear fuel cycle. Moreover, N-rich TcN₃ and TcN₄ exhibit remarkable bulk properties and can be potential ultrastiff and hard materials.Нітриди технеція з різною ідеальної стехіометрією досліджені із застосуванням методу перших принципів при тисках від 0 до 60 ГПа. Встановлено, що може бути багато стабільних нітридів технеція, включаючи Tc₃N, Tc₂N, ТКС, Tc₂N₃, TcN₂, TcN₃ і TcN₄, серед яких субнітриди Tc₃N і Tc₂N синтезуються при нульовому тиску і можуть бути використані для обробки ядерних відходів, таких як виділений при ядерному паливному циклі радіоактивний 99Tc. Більш того, TcN₃ і TcN₄, збагачені N, демонструють чудові об’ємні властивості і можуть бути потенційними ультражорсткими і твердими матеріалами.Нитриды технеция с различной идеальной стехиометрией исследованы с применением метода первых принципов при давлениях от 0 до 60 ГПа. Установлено, что может быть много стабильных нитридов технеция, включая Tc₃N, Tc₂N, ТКС, Tc₂N₃, TcN₂, TcN₃ и TcN₄, среди которых субнитриды Tc₃N и Tc₂N синтезируются при нулевом давлении и могут быть использованы для обработки ядерных отходов, таких как выделенный при ядерном топливном цикле радиоактивный 99Tc. Более того, TcN₃ и TcN₄, обогащенные N, демонстрируют замечательные объемные свойства и могут быть потенциальными ультражесткими и твердыми материалами

Superparamagnetic behavior in Fe ultrathin films on GaN(0001)

In this paper, growth, structural and magnetic properties of ultrathin Fe grown on GaN(OOOl) by molecular beam epitaxy. The films and their surfaces were monitored by in-situ reflection high energy electron diffraction (RHEED) and a crystal thickness monitor. The magnetic properties of the samples were determined by a superconducting quantum interference device (SQUID) magnetometer. Superparamagnetism (SPM) of the ultrathin Fe can be activated at the ambient temperature.the hysteresis loop of an as-deposited 5 ML Fe(llO) film on GaN(0001) taken at RT and reveals that the loop on one hand has an unsaturated magnetization and on the other hand possesses tiny but noticeable Mr and Hc. These two characteristics as a whole imply a coexistence of SPM and weak FM in the ultrathin film. In order to gain further insight into this mixed magnetic state, temperature dependence of the magnetization M(T) in the form of field cooling (FC) and zero field cooling (ZFC) curves of the 5 ML sample was measured by SQUID in a T range between 5 and 300 K

Strategies for Controlled Placement of Nanoscale Building Blocks

The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others

Galaxy Clusters Associated with Short GRBs. II. Predictions for the Rate of Short GRBs in Field and Cluster Early-Type Galaxies

We determine the relative rates of short GRBs in cluster and field early-type galaxies as a function of the age probability distribution of their progenitors, P(\tau) \propto \tau^n. This analysis takes advantage of the difference in the growth of stellar mass in clusters and in the field, which arises from the combined effects of the galaxy stellar mass function, the early-type fraction, and the dependence of star formation history on mass and environment. This approach complements the use of the early- to late-type host galaxy ratio, with the added benefit that the star formation histories of early-type galaxies are simpler than those of late-type galaxies, and any systematic differences between progenitors in early- and late-type galaxies are removed. We find that the ratio varies from R(cluster)/R(field) ~ 0.5 for n = -2 to ~ 3 for n = 2. Current observations indicate a ratio of about 2, corresponding to n ~ 0 - 1. This is similar to the value inferred from the ratio of short GRBs in early- and late-type hosts, but it differs from the value of n ~ -1 for NS binaries in the Milky Way. We stress that this general approach can be easily modified with improved knowledge of the effects of environment and mass on the build-up of stellar mass, as well as the effect of globular clusters on the short GRB rate. It can also be used to assess the age distribution of Type Ia supernova progenitors.Comment: ApJ accepted versio