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Studium tantalu pomocí potenciálů typu bond-order
Čák, Miroslav ; Mrověc, M. ; Vitek, V. ; Šob, Mojmír
We present a bond-order potential (BOP) study for the bcc transition metal tantalum. The BOPs are a real-space semiempirical scheme for the description of interatomic interactions based on the tight-binding approximation. The potentials are applied to the calculation of total energy profile along the tetragonal deformation path and gamma-surface of {110} plane. Our results are in a good agreement with the ab initio calculated values which indicates that BOPs are capable to describe properly the bonding in bcc transition metals.
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Nanoindentation and theoretical strength in metals and intermetallics
Šob, Mojmír ; Legut, Dominik ; Friák, Martin ; Fiala, J. ; Vitek, V. ; Hafner, J.
The present contribution gives an account of applications of quantum-mechanical (first-principles) electronic structure calculations to the problem of theoretical strength in metals and intermetallics. First, we briefly describe the way of simulating the tensile test and the electronic structure calculational method. Then we discuss the theoretical strength values in a number of elemental metals and intermetallics and compare them with available experimental data, both from measurements on whiskers and from nanoindentation experiments.
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Structure and magnetism of iron and iron overlayers from the first principles
Friák, Martin ; Šob, Mojmír ; Vitek, V.
A detailed theoretical study of magnetic behavior of iron along the bcc fcc (Bain's) transformation paths at various atomic volumes is presented. The total energies are calculated by spin polarized full potential LAPW method and are displayed in contour plots as functions of tetragonal distortion c/a and volume; borderlines between various magnetic phases are shown. Stability of tetragonal magnetic phases of fl Fe is discussed. The calculated phase boundaries are used to predict the lattice parameters and magnetic states of iron overlayers on various (001) substrates.
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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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Ab initio study of displacive phase transformations in iron
Friák, Martin ; Šob, Mojmír ; Wang, L. G. ; Vítek, V.
The bcc-hcp and bcc-fcc transformations in iron are studied ab initio by following a constant-volume one-parameter transformation paths. Calculation make it possible to locate, the transition configuration at which the bcc ferromagnetic structure transforms into the hcp nonmagnetic structure as well as the transition from the high-spin state to a low-spin state along the bcc-fcc transformation path.
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