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Phase Equilibria in Systems for Lead-Free Solders
Vřešťál, J. ; Kroupa, Aleš ; Zemanová, Adéla ; Houserová, J. ; Pinkas, J.
In the year 2006,the optimization of parameters of systems Bi-Pd and Ag-In-Pd were completed by publications in articles and by addud of parameters to database COST 531. The optimisation of parameters for calculation of phase diagram of system Bi-Sb-Sn and In-Sb-Sn was performed and the results were publiced in Journal of Alloys and Compounds and parameters were added to database COST 531 and the optimisation of parameters in the system Cu-In-Sn was developing.
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Analýza elektronové struktury Lavesových fází obsahujících chrom
Houserová, Jana ; Šob, Mojmír
Binary systems containing chromium can be found in many kinds of steels where the Laves-phase can be considered as a potential candidate for strengthening provided size and distribution of the particles are within certain limits. We performed electronic structure calculations to study the thermodynamic and structural properties of the C14 Laves phase with various compositions. In the frame of the thermodynamic study, we have evaluated the total energies of formation of Laves phase structure with different occupations of sublattices (Cr2Cr, Cr2X, X2Cr, X2X, where X stands for Fe, Mo, Si, Ta and W) with respect to the Standard Element Reference (SER) states. These energies of formation are of great importance for prediction of stability of studied configurations.
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Energetika tvorby sigma fází v Mo-X (X=Co, Cr, Fe) systémech
Houserová, Jana ; Šob, Mojmír
In systems Mo-Co, Mo-Cr and Mo-Fe, we performed calculations of the total energies of formation of all 32 possible occupations of sublattices in sigma phase structure. The optimisation of the lattice parameters of all structures was included. Sigma phases in studied systems exhibit positive values of energies of formation and it is supposed that the stability of the really existing sigma phases (i.e. Mo-Fe and Mo-Co) is due to configurational and vibrational entropies.
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Ab initio studie Lavesových fází v systémech Fe-Cr, Fe-Mo a Fe-Ta
Houserová, Jana ; Šob, Mojmír
Binary systems Fe-Cr, Fe-Mo and Fe-Ta can be found in many kinds of steels where the Laves-phase can be considered as a potential candidate for strengthening provided size and distribution of the particles are within certain limits. We performed electronic structure calculations to study the thermodynamic and structural properties of the C14 Laves phase with various compositions. In the frame of the thermodynamic study, we have evaluated the total energies of formation of Laves phase structure with different occupations of sublattices (Fe2Fe, Fe2X, X2Fe, X2X, where X stands for Cr, Mo and Ta) with respect to the Standard Element Reference (SER) states. These energies of formation are of great importance for prediction of stability of studied configurations.
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Calculations of Energetics of Sigma Phase Formation and Thermodynamic Modelling in Fe-Ni-Cr System
Chvátalová, K. ; Houserová, Jana ; Šob, Mojmír ; Vřešťál, J.
The energy of formation of sigma phase with respect to standard reference structures of pure constituents were calculated using the combination of LMTO-ASA and FLAPW method for Ni-Fe and Ni-Cr systems. All results are based on the equilibrium lattice parameters of included structures. Calculated energies of formation of sigma phase of pure constituents were used for the thermodynamic modelling of the ternary system Fe-Ni-Cr. The calculated phase diagram agrees well with experimental data. Enthalpies of formation of sigma phase in Ni-Cr and in Ni-Fe obtained by thermodynamic modelling agree with the energy of formation calculated ab initio.
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Ab-Initio Calculated Energetics of Sigma Phase in Mo-Fe and Mo-Co Systems
Houserová, Jana ; Šob, Mojmír ; Vřešťál, J.
It is shown that first-principles electronic structure calculations may be used to estimate the energy of formation of sigma-phase in molybdenum-based systems. The calculations are performed with the help of the linear muffin-tin orbital method in the atomic sphere approximation (LMTO-ASA) and the full-potential linear augmented plane wave (FLAPW) method. The exchange-correlation energy is evaluated within the general gradient approximation (GGA).
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