|
|
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.
|
|
|
Si-obsahující Lavesovy fáze
Houserová, Jana
We performed electronic structure calculations to study the thermodynamic and structural properties of the C14 Laves phases in several systems with various compositions. In the frame of a thermodynamic study, we have evaluated the total energies of formation of Laves phase structure with different occupations of sublattices (Si2Si, Si2X, X2Si, X2X, where X stands for Cr, Fe, Mo and W) with respect to the Standard Element Reference (SER) states.
|
|
| |
|
| |
|
| |
|
|
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.
|
|
|
Ab initio simulation of three-axial deformation of perfect iron crystal
Černý, M. ; Šandera, P. ; Pokluda, J. ; Friák, Martin ; Šob, Mojmír
Ab initio electronic structure calculations of ideal strength, bulk modulus and equilibrium lattice parameter of iron in the body-centered-cubic lattice under three-axial tension are performed using the linear muĆn-tin orbitals method in atomic sphere ap proximation (LMTO-ASA) and the full-potential linearized augmented plane waves method (FLAPW). Magnetic ordering was taken into account by means of spin-polarized calculation. Two exchange-correlation energy approximations were employed, namely the local (spin) den-sity approximation (LDA) and the generalized gradient approximation (GGA). Computed values are compared with experimental data.
|
|
| |
|
| |
guest ::
