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Study of inter-atomic interactions in advanced materials with help of ab initio calculations
Janovec, Jozef ; Šob, Mojmír (oponent) ; Zelený, Martin (vedoucí práce)
Chemical bonding in transition metal diborides and Ni2MnGa alloy was studied in terms of energy resolved COHP visualization tool. The electronic structure of studied systems was calculated using the first principles calculations with the help of projector augmented-wave method. Concerning transition metal diborides, we found dependence of the strongest boron-boron bond on the charge transfer from metal to boron atoms. The stability of diborides with the alpha structure decreases with higher number of metal valence electrons due to on-site contribution to the band energy near the Fermi level. Ni2MnGa shape memory alloy was treated by DFT+ U corrective method in order to describe localized electrons more accurately. The effect of U on Ni resides in destabilization of the cubic austenite and stabilization of the tetragonal NM martensite. On the contrary, U on Mn destabilizes martensite. The bond analysis shows that the strongest bond in the alloy is Ni-Ga with covalnet character. Increased localization of Mn valence electrons makes Mn-Ni bond more covalent and Ni-Ni bond more metallic. The localization of Ni electrons results in more metallic Mn-Ni bond.
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Analýza chemických vazeb ve slitinách pomocí dolování dat
Nechutová, Vendula ; Šeda, Miloš (oponent) ; Roupec, Jan (vedoucí práce)
Práce se zabývá aplikací metod Data miningu pro analýzu dvou mřížek Ni3Si, jedna se stabilní hranicí zrn a druhá s nestabilní hranicí zrn. Zkoumají se zde křivky DOS a COHP pomocí vybraných metod pro porovnávání křivek. Okolí jednotlivých atomů se vyšetřuje pomocí Voroného diagramu. Tyto informace se pak využijí k odhalení rozdílů ve vazbách mezi stabilní a nestabilní mřížkou.
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Study of inter-atomic interactions in advanced materials with help of ab initio calculations
Janovec, Jozef ; Šob, Mojmír (oponent) ; Zelený, Martin (vedoucí práce)
Chemical bonding in transition metal diborides and Ni2MnGa alloy was studied in terms of energy resolved COHP visualization tool. The electronic structure of studied systems was calculated using the first principles calculations with the help of projector augmented-wave method. Concerning transition metal diborides, we found dependence of the strongest boron-boron bond on the charge transfer from metal to boron atoms. The stability of diborides with the alpha structure decreases with higher number of metal valence electrons due to on-site contribution to the band energy near the Fermi level. Ni2MnGa shape memory alloy was treated by DFT+ U corrective method in order to describe localized electrons more accurately. The effect of U on Ni resides in destabilization of the cubic austenite and stabilization of the tetragonal NM martensite. On the contrary, U on Mn destabilizes martensite. The bond analysis shows that the strongest bond in the alloy is Ni-Ga with covalnet character. Increased localization of Mn valence electrons makes Mn-Ni bond more covalent and Ni-Ni bond more metallic. The localization of Ni electrons results in more metallic Mn-Ni bond.
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Analýza chemických vazeb ve slitinách pomocí dolování dat
Nechutová, Vendula ; Šeda, Miloš (oponent) ; Roupec, Jan (vedoucí práce)
Práce se zabývá aplikací metod Data miningu pro analýzu dvou mřížek Ni3Si, jedna se stabilní hranicí zrn a druhá s nestabilní hranicí zrn. Zkoumají se zde křivky DOS a COHP pomocí vybraných metod pro porovnávání křivek. Okolí jednotlivých atomů se vyšetřuje pomocí Voroného diagramu. Tyto informace se pak využijí k odhalení rozdílů ve vazbách mezi stabilní a nestabilní mřížkou.
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