National Repository of Grey Literature 23 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Studies of structural and magnetic properties of iron nanowires from first principles
Zelený, Martin ; Šob, Mojmír ; Hafner, J.
In this work we study the structure and stability of iron ultrathin free-standing nanowires by first-principles density functional approach. For total energy calculations, we use the Vienna ab initio Simulation Package (VASP) in the projector augmented-wave (PAW) representation. The evolution of electronic structure and magnetism of iron chains as a function of compression and stretch is investigated. The forming of different types of structures is analyzed: simple linear chain, dimerized chain, ideal two-dimensional (2D) zig-zag structure relaxed in x and y directions, fully relaxed 2D structure, and three-dimensional (3D) structure with tetrahedral arrangements. It turns out that the structure of iron nanowires and types of interatomic bonds are strongly dependent on their stretch or compression.
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.
Transition between close-packed structures in palladium
Káňa, Tomáš ; Hüger, E. ; Šob, Mojmír
Possible mechanisms of hcp-fcc phase transition in Pd are studied with the help of ab initio electronic structure calculations.
Studium elektronové struktury a krystalických fází teluru z prvních principů
Hemzalová, P. ; Legut, Dominik ; Šob, Mojmír
We study the energetics of seven crystalline phases of tellurium (trigonal, rhombohedral, orthorhombic, monoclinic, simple cubic, body-centered cubic and face-centered cubic phase) from first principles in order to reveal the relation between them and to advance our fundamental understanding of behavior of tellurium at high pressures.
Elektronová struktura slitin india a cínu
Všianská, Monika ; Legut, Dominik ; Šob, Mojmír
The In-Sn system is interesting due to the existence of the simple hexagonal (sh) structure for compositions from 75 to 87 at% Sn at 25 ºC and from 73 to 85 at% Sn at -150 ºC. These alloys are usually referred to as gamma-Sn. Here we study the electronic structure and total energy of gamma-Sn with the help of virtual crystal approximation and demonstrate that sh structure has the lowest energy in the interval of existence of gamma-tin.
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.
Electronic structure In-Sn alloys
Všianská, Monika ; Legut, Dominik ; Šob, Mojmír
The InSn system is interesting by the existence of a simple hexagonal phase for compositions from 72 to 87 at% Sn at 25 °C and from 73 to 85 at% Sn at -150 °C. These alloys are usually referred to as gamma–Sn. The InSn alloys are disordered in the whole concentration interval. In this contribution, energetics and electronic structure of InSn system is studied from first principles. A simplified version of virtual crystal approximation is employed to describe disorder. It turns out that the present approach is capable of describing phase composition of InSn system in the whole concentration interval. In particular, we are able to reproduce the existence of simple hexagonal phase around 80 at% Sn.
Grain boundary magnetism - ab initio study
Čák, Miroslav ; Šob, Mojmír ; Hafner, J.
We study the magnetic structure of the symmetrical tilt grain boundary sigma 5 (310) in iron. It is shown, that local magnetic moments of atoms at grain boundary is enhanced when compared to the bulk value. This is interpreted as a magnetovolume effect.
Ab initio studie magnetismu Ni a Co podél trigonální deformační dráhy
Zelený, Martin ; Šob, Mojmír
We have calculated the total energies of nickel and cobalt as a function of volume and trigonal deformation for various magnetic phases and found the phase boundaries between the FM and NM modifications. The calculated contour plots can be used for the understanding and prediction of lattice parameters and magnetic states of Ni and Co thin films on various fcc (111) metallic substrates.
Energetika strukturních změn MoSi2
Káňa, Tomáš ; Legut, Dominik ; Šob, Mojmír
We employed ab initio calculations to investigate total energy profiles along the transformation paths connecting the C11b, C40 and C54 structures in MoSi2. The transformations were realized by change of the stacking sequence of the atomic planes. We found that the total energy profiles of the proposed paths have high energy barriers between end-point structures: 1.4 eV/f.u (f.u is the formula unit) for the C40-C54 path, 1.8 eV/f.u for the C11b-C40 path and finally 2.5 eV/f.u. for the C11b-C54 path.

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