Structural stability of ternary D8(m)-Ti5Sb2X (X=Al, Ga, In, Si, Ge, Sn) compounds

International audienceThe crystal and electronic structures of Ti5Sb2X (X=Al, Ga, In, Si, Ge, Sn) ternary compounds in the Nb5Sn2Si-type structure (ternary-D8(m)) have been investigated by means of first principles calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the Ti5Sb2X (X=Al, Ga, In, Si, Ge, Sn) ternary compounds in the ternary D8(m) structure. The enthalpies of formation of the ternary D8(m) compounds have been obtained. The off-stoichiometry domains of D8(m)-Ti5Sb2Ga and D8(m)-Ti5Sb2Si are discusse

First principles calculations in V-Si system. Defects in A15-V3Si phase

International audienceThe structural and thermodynamic properties of vanadium silicides have been obtained from DFT calculations. The calculated values of the enthalpies of formation and of the lattice parameters at T = 0 K agree well with the experimental values. We have studied the defects in the A15-V3Si compound and found that the dominant defects are antisites. Using a simple statistical model, the atomic defects concentrations and the corresponding thermodynamic data have been obtained. The enthalpies of mixing of V and Si on the two sublattices of the A15 structure have been obtained from total energy of A15 supercells. In order to describe the equilibrium between the A15 phase and the A2 solid solution based on vanadium, calculations of the enthalpy of mixing of the A2 solid solution have been performed by using supercells and special quasi random structures. The V-rich part of the V-Si phase diagram has been calculated using the data obtained from ab intio total energy calculations. (C) 2013 Elsevier B.V. All rights reserved

First principles calculations of the stability of the T2 and D8(8) phases in the V-Si-B system

International audienceThe crystal and electronic structures of D8(1)-V5SiB2 and D8(8)-V5Si3B ternary compounds have been investigated by means of first principle calculations. The calculated structural parameters are in very good agreement with the experimental data. The calculated values of the enthalpies of formation at T = 0 K of the D8(1)-V5SiB2 and D8(8)-V5Si3B ternary compounds are -67.1 and -62.1 kJ/mol of atoms respectively. The total and partial electronic densities of states show a strong hybridization between the B p states and V d states. The defect enthalpies of formation as well as the mixing enthalpies have been computed. These data are essential for the modeling of the D8(1) and D8(8) phases in the V Si B ternary system. A partial V-VSi2-VB isothermal section at 298 K is proposed. (C) 2014 Elsevier Ltd. All rights reserved

Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

International audienceThe enthalpies of formation of transition metals diborides in various structures have been obtained from density functional theory (DFT) calculations in order to determine the ground state at T = 0 K and p = 0. The evolution of the enthalpies of formation along the 3D, 4D, and 5D series has been correlated to the considered crystal structures. In the whole, the calculated values of the enthalpies of formation of the diborides in their ground state are in good agreement with the experimental ones when available. The calculated values of the lattice parameters at T = 0 K of the ground state agree well with the experimental values. The total and partial electronic densities of states have been computed. Special features of the transition metal electronic partial density of states have been evidenced and correlated to the local environment of the atoms

Mechanical alloying of a new promising thermoelectric material, Sb3Zn4

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Phase transformations in the Zn–Cd–Sb system

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Phase equilibria in the Cr-Si-Ti system below 40 at.% Si

Highlights• Phase relations in Cr-Si-Ti system have been studied experimentally.• Partial liquidus and solidus projections have been constructed.• Partial isothermal sections at 1450, 1150 °C, isopleths at 10 at.% Si, 50 at.% Ti were constructed.• γTiCr2 is stabilized by additions of Si, and in the ternary system melts congruently at >1600 °C.International audiencePhase transformations in the Cr-Si-Ti ternary system have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) at silicon content <40 at.%. Partial liquidus and solidus projections and the melting diagram (solidus + liquidus) have been constructed. Some sections as partial isothermal at 1450 and 1150 °C, isopleths at 10 at.% Si and 50 at.% Ti are described. The liquidus surface is characterized by the presence of primary crystallization regions of a solid solution (Cr,βTi) and binary based phases (Cr3Si), (Ti5Si5) and the Laves-phase C14, which is stabilized by additions of silicon, and in the ternary system melts congruently above 1600 °C. The solidus surface is characterized by the presence of three-phase fields: (γTiCr2) + (Cr3Si) + (Cr,βTi), (Ti5Si3) + (γTiCr2) + (βTi,Cr) and (Ti5Si3) + (γTiCr2) + (Cr3Si). The former two regions form invariant four-phase eutectic equilibria L ↔ (βTiCr2) + (Cr3Si) + (Cr,βTi) and L ↔ (Ti5Si3) + (γTiCr2) + (βTi,Cr) at 1534 and 1243 °C, respectively. The maximum of the solidus temperature of about 1580 °C is observed in the field (γTiCr2) + (Cr,βTi). At 1495 °C the solid-state transformation (γTiCr2) + (Cr3Si) ↔ (Ti5Si3) + (Cr,βTi) takes place

Phase transformations and phase equilibria in the Co–Sn–Ti system in thecrystallization interval

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Chemical route for formation of intermetallic Zn4Sb3 phase

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