A theoretical study of the structural phases of Group 5B - 6B metals and their transport properties

In order to predict the stable and metastable phases of the bcc metals in the block of the Periodic Table defined by groups 5B to 6B and periods 4 to 6, as well as the structure dependence of their transport properties, we have performed full potential computations of the total energies per unit cell as a function of the c/a ratio at constant experimental volume. In all cases, a metastable body centered tetragonal (bct) phase was predicted from the calculations. The total energy differences between the calculated stable and metastable phases ranged from 0.09 eV/cell (vanadium) to 0.39 eV/cell (tungsten). The trends in resistivity as a function of structure and atomic number are discussed in terms of a model of electron transport in metals. Theoretical calculations of the electrical resistivity and other transport properties show that bct phases derived from group 5B elements are more conductive than the corresponding bcc phases, while bct phases formed from group 6B elements are less conductive than the corresponding bcc phases. Special attention is paid to the phases of tantalum where we show that the frequently observed beta phase is not a simple tetragonal distortion of bcc tantalum

The effect of crystallization conditions on tantalum distribution in molybdenum and tungsten during electron beam zone melting

The distribution of tantalum in molybdenum and tungsten single crystals during electron beam floating zone melting under different crystallization conditions was investigated. The performed line chemical analysis of specimens proved creation of tantalum micro segregation, so-called growth striations, which showed themselves on concentration profiles as periodically alternating areas with increased and decreased concentrations of tantalum. The existence of these chemical inhomogeneities suggests that stationary conditions of the crystal growth were disturbed during the zone melting, i.e. fluctuations of microscopic rate of growth occurred due to convection in the melt. The determined effective distribution coefficients of tantalum in molybdenum and tungsten approach to calculated theoretical values of the equilibrium distribution coefficient

Особливості перекладу адвербіальних дієслів руху

Проаналізовано парадигматичні та синтагматичні характеристики адвербіальних дієслів руху. Встановленно розходження при перекладі дієслів з експліцитною й імпліцитною семою руху. Переклад на рівні варіантних відповідників домінує при передачі дієслів з експліцитною семою; переклад на рівні контекстуальних замін притаманний дієсловам з імпліцитною семою. Paradigmatic and syntagmatic properties of adverbial verbs of motion were analysed. Differences in conveying verbs with explicit and implicit semes of motion were established. Translation on the level of variational correspondences is predominant when rendering verbs with explicit seme; translation on the level of contextual substitutions is typical of verbs with implicit seme

Special competence in the structure of vocational pedagogical integrity in the sphere of vocational education

The significance of the issue under study lies in research of the subject matter, character and components of special competences, as well as defining feasible ways of their formation in the framework of a higher vocational pedagogical institution. The article is aimed at providing the rationale for necessary formation of special competences in education for vocational teachers with implementation of Vocational and Federal State Education Standards. The main method of studying the given issue consists in pedagogical modeling of educational procedures for vocational teachers which allows it to outline the formation process of a special competence in learning specialist disciplines after determining its structure and contents. It was deemed necessary and proved to form special competence in education of future vocational teachers. The process of special training was structured with relevant amendments and supplements to its contents. On the top of it, this process of was accompanied by specially designed learning and teaching materials. The contents of the article could be of interest for graduate students and postgraduates as well as teachers who are involved in working on educational projects for vocational teachers. © Authors

Structural and magnetic properties of the (001) and (111) surfaces of the half-metal NiMnSb

Using the full potential linearised augmented planewave method we study the electronic and magnetic properties of the (001) and (111) surfaces of the half-metallic Heusler alloy NiMnSb from first-principles. We take into account all possible surface terminations including relaxations of these surfaces. Special attention is paid to the spin-polarization at the Fermi level which governs the spin-injection from such a metal into a semiconductor. In general, these surfaces lose the half-metallic character of the bulk NiMnSb, but for the (111) surfaces this loss is more pronounced. Although structural optimization does not change these features qualitatively, specifically for the (111) surfaces relaxations can compensate much of the spin-polarization at the Fermi surface that has been lost upon formation of the surface.Comment: 18 pages, 8 figure