Ab Initio Calculations for Properties of Laves Phase V2m (M = Zr, Hf, Ta) Compounds

Chihi, T.

doi:10.11648/j.ajmp.20130202.20

Cited by 10 publications

(7 citation statements)

References 13 publications

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“…Nevertheless, the phase formation data obtained in this work are consistent with the experimentally reported sequence of phases as a function of temperature measured by high-resolution synchrotron X-ray diffraction [5]. In addition, comparable DFT results were reported for cubic C15 ZrV 2 , which is stable above 116 K [29,30], for which, to the best of our knowledge, exclusively positive energies of formations are reported [26,31,32].…”

Section: Ground State Stabilitysupporting

confidence: 91%

“…While some report that the cubic HfV 2 structure exhibits negative energies of formation of −15.7 [14] and −18.0 meV/atom [15] 2 of 12 in the ground state, others obtain positive energies of formation of 31.0 [27] and 34.8 meV/atom [28], respectively. Furthermore, theoretical studies conducted for cubic C15 ZrV 2 , as the stable phase above 116 K [29,30], yield solely positive energies of formation [26,31,32].…”

Section: Introductionmentioning

confidence: 99%

“…Numerous first-principle calculations have been performed to study HfV 2 [14][15][16]25,26], leading to controversial results regarding the stability of the cubic C15 structure. While some report that the cubic HfV 2 structure exhibits negative energies of formation of −15.7 [14] and −18.0 meV/atom [15] 2 of 12 in the ground state, others obtain positive energies of formation of 31.0 [27] and 34.8 meV/atom [28], respectively.…”

Section: Introductionmentioning

confidence: 99%

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Temperature and Impurity Induced Stabilization of Cubic HfV2 Laves Phase

et al. 2019

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The stability of cubic HfV2 (Fd3m) was investigated as a function of temperature as well as interstitially solved oxygen and hydrogen using density functional theory. Mechanical and energetic instability of pristine cubic HfV2 is obtained in the ground state at 0 K, which is unexpected as it can readily be synthesized. Combined Debye–Grüneisen and electronic entropy calculations indicate that HfV2 is stabilized with increasing temperature primarily as a result of lattice vibrations. In contrast, temperature-induced mechanical stabilization, considering the Born stability criteria, is achieved due to the electronic entropy. Interstitial incorporation of hydrogen and oxygen into the cubic structure contributes to the energetic and mechanical stabilization in the ground state for impurity concentrations as low as 1 at%, owing to strong ionic/covalent bond formation with the matrix atoms.

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Section: Ground State Stabilitysupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temperature and Impurity Induced Stabilization of Cubic HfV2 Laves Phase

et al. 2019

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“…As can be seen, the calculations are within the uncertainty range of the experimental data. Figure 4 b shows the calculated enthalpy of formation in the Ta-Cr system at 0 and1693 K, and the measured data [ 73 ] and DFT calculations [ 54 , 56 , 73 , 74 , 75 ] are also appended for a comparison. The calculated enthalpy formation of the C15 phase at 1693 K has a nice agreement with that from measurement [ 73 ].…”

Section: Resultsmentioning

confidence: 99%

Third-Generation Thermodynamic Descriptions for Ta-Cr and Ta-V Binary Systems

Zhang

Chen

et al. 2022

Materials

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The third-generation thermodynamic descriptions for Ta-Cr and Ta-V binary systems were performed to construct the reliable thermodynamic database for refractory high-entropy alloys (RHEAs) containing Laves phase. The third-generation Gibbs energy expressions of pure Cr and V in both solid and liquid phases were established, from which the thermodynamic properties and thermal vacancy can be well described. The thermodynamic descriptions of Ta-Cr and Ta-V over the whole composition and temperature regions were carried out based on the reviewed phase equilibria and thermodynamic data with the CALPHAD (CALculation of PHAse Diagrams) approach. Specifically, the thermodynamic parameters of C14 and C15 Laves phases were evaluated by combining the theoretically computed and experimentally measured thermodynamic properties as well as the semiempirical relations. The calculated phase diagrams and thermodynamic properties in Ta-Cr and Ta-V systems according to the present thermodynamic parameters had a nice agreement with the experimental data even down to 0 K, indicating the reliability of the present modeling.

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“…The intermediate formation of bcc V and hcp Zr is contradictive to the accepted equilibrium phase diagram and is mostly discussed with respect to difficult nucleation kinetics of the Laves phase structure [69,70]. However, it may also be explained by the thermodynamic instability of cubic ZrV 2 , as predicted by DFT in the ground state [71][72][73], exhibiting an energy of formation of 150 meV atom −1 [71], which persists at elevated temperatures. In comparison, several theoretical studies also predict cubic HfV 2 to be energetically unstable in the ground state, reporting energies of formation between 20 and 35 meV per atom [29,74,75].…”

Section: Phase Formation Of Hfvmentioning

confidence: 99%

A Proposal for a Composite with Temperature-Independent Thermophysical Properties: HfV2–HfV2O7

et al. 2020

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The HfV2–HfV2O7 composite is proposed as a material with potentially temperature-independent thermophysical properties due to the combination of anomalously increasing thermoelastic constants of HfV2 with the negative thermal expansion of HfV2O7. Based on literature data, the coexistence of both a near-zero temperature coefficient of elasticity and a coefficient of thermal expansion is suggested for a composite with a phase fraction of approximately 30 vol.% HfV2 and 70 vol.% HfV2O7. To produce HfV2–HfV2O7 composites, two synthesis pathways were investigated: (1) annealing of sputtered HfV2 films in air to form HfV2O7 oxide on the surface and (2) sputtering of HfV2O7/HfV2 bilayers. The high oxygen mobility in HfV2 is suggested to inhibit the formation of crystalline HfV2–HfV2O7 composites by annealing HfV2 in air due to oxygen-incorporation-induced amorphization of HfV2. Reducing the formation temperature of crystalline HfV2O7 from 550 °C, as obtained upon annealing, to 300 °C using reactive sputtering enables the synthesis of crystalline bilayered HfV2–HfV2O7.

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Ab Initio Calculations for Properties of Laves Phase V2m (M = Zr, Hf, Ta) Compounds

Cited by 10 publications

References 13 publications

Temperature and Impurity Induced Stabilization of Cubic HfV2 Laves Phase

Temperature and Impurity Induced Stabilization of Cubic HfV2 Laves Phase

Third-Generation Thermodynamic Descriptions for Ta-Cr and Ta-V Binary Systems

A Proposal for a Composite with Temperature-Independent Thermophysical Properties: HfV2–HfV2O7

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