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Structure and magnetism of clean and impurity-decorated grain boundaries in nickel from first principles
Všianská, Monika ; Šob, Mojmír
We present a detailed theoretical study of segregation of sp-elements from the 3rd-5th period (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) in fcc FM Ni. Whereas there is a slight enhancement of magnetization at the clean GB and FS with respect to bulk nickel (3–7% and 24%, respectively), the studied impurities entirely kill or strongly reduce ferromagnetism at the GB so that magnetically dead layers are formed. We determine the preferred segregation sites at the GB for the impurities studied, their segregation enthalpies and strengthening/embrittling energies. We find interstitially segregated Si and P and substitutionally segregated Al as a GB cohesion enhancer, and interstitially segregated S, Ge, As, Se and substitutionally segregated Ga, In, Sn, Sb and Te as GB embrittlers in Ni. As there is very little experimental information on GB segregation in nickel most of the present results are theoretical predictions which may motivate future experimental work.
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Innovated set for demonstrative experiments from electronics
VAŠÍČEK, Petr
The first part of this thesis is focused on the advantages of using the experiments during the physics education and their educational values. Furthermore, some types of experiments, their correct metodology of implementation and some other aspects which should be given an appropriate attention by the teacher are theoretically described. Then, some types of demonstrational sets and their brief history are described. The attention is aimed at the demonstrational set of DIDAKTIK, its content and composition. One chapter is devoted to the research of schools equipment for using the demonstrational experiments of electricity and magnetism and their evaluations. The last part deals with some experiments which can be made within this set, their documentation and evaluation. Further, there were worksheets created for some of these experiments. Two of these sheets were used among primary schools for didactic exploring and the reasults were evaluated.
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Physical practicum - electronic support of education
GRILL, František
This thesis is concerned with promoting physical education practicum course. The first section describes the basic knowledge, skills and detailed instructions for creating and processing of measurement reports. The second part is divided into the different roles of physics - Mechanics and thermodynamics, Electricity and magnetism, Oscillations, waves and optics, Electronics, Atomic physics and Special measurements. The third section provides a brief description of the created web sites, their organization and content.
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Studium magnetismu hranic zrn z prvních principů
Čák, Miroslav ; Šob, Mojmír ; Hafner, J.
Grain boundaries (GBs) represent an important class of two-dimensional extended defects in materials. Segregation of impurity atoms is responsible for a degradation of mechanical properties. Recently, it was found that application of magnetic annealing leads to decreasing concentration of impurities at GBs in Fe-0.8%Sn alloy and improves its ductility To understand the mechanism of this process it is necessary to study magnetism of clean GBs as well as of GBs with segregants at the microscopic (ab initio) level. In the present work, we investigate the Sigma5(310) GB in iron.
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Ab initio simulation of a tensile test in iron
Friák, Martin ; Šob, Mojmír ; Vitek, V.
A tensile test in ferromagnetic and nonmagnetic iron is simulated by ab initio electronic structure calculations using all-electron full potential linearized augmented plane wave method (FLAPW) within generalized gradient approximation (GGA). The theoretical tensile strength of ferromagnetic iron for [001] loading is determined and compared with that of other materials. The magnetic behavior of iron under tensile loading is studied in detail and compared with results for triaxial loading.
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