Coupling of lattice dynamics and configurational disorder in metal deficient Al1−<i>δ</i>B2 from first-principles

Johansson, Erik; Eriksson, Fredrik; Ektarawong, Annop; Rosén, Johanna; Alling, Björn

doi:10.1063/5.0047275

Cited by 10 publications

(8 citation statements)

References 53 publications

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“…Also, in the present work, all tantalum atoms, residing on the metal sublattice of α−TaB 2−x , are presumed to be mere spectators, and therefore they do not participate in the procedure of cluster expansion. The explanation on how the cluster-expansion method is implemented to search for low-energy configurations of any substitutional solid solution can be found, for example, in [12,[40][41][42].…”

Section: Cluster-expansion Methodsmentioning

confidence: 99%

“…By following the cluster-expansion procedure provided, for example, in [12,[40][41][42], the final set of the effective cluster interactions is determined by fitting the total energies of 108 unique configurations of α−TaB 2−x with the leave-one-out cross validation score of 28.75 meV/f.u., see also figure 3(a) showing the error distribution of the fit, and it is composed of 19 2-site and 12 3-site interactions. The interactions are also employed to predict the energies of the remaining 742 configurations.…”

Section: In Search Of Ground-state Structures Of α−Tab 2−xmentioning

confidence: 99%

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Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB₂-type tantalum diborides as revealed by first-principles calculations

Ektarawong

Johansson²,

Pakornchote

et al. 2023

J. Phys. Mater.

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Thermodynamic stability as well as structural, electronic, and elastic properties of boron-deficient AlB$_{2}$-type tantalum diborides, which is designated as $\alpha$$-$TaB$_{2-x}$, due to the presence of vacancies at its boron sublattice are studied $via$ first-principles calculations. The results reveal that $\alpha$$-$TaB$_{2-x}$, where 0.167 $\lesssim$ $x$ $\lesssim$ 0.25, is thermodynamically stable even at absolute zero. On the other hand, the shear and Young's moduli as well as the hardness of stable $\alpha$$-$TaB$_{2-x}$ are predicted to be superior as compared to those of $\alpha$$-$TaB$_{2}$. The changes in the relative stability and also the elastic properties of $\alpha$$-$TaB$_{2-x}$ with respect to those of $\alpha$$-$TaB$_{2}$ can be explained by the competitive effect between the decrease in the number of electrons filling in the antibonding states of $\alpha$$-$TaB$_{2}$ and the increase in the number of broken bonds around the vacancies, both induced by the increase in the concentration of boron vacancies. A good agreement between our calculated lattice parameters, elastic moduli and hardness of $\alpha$$-$TaB$_{2-x}$ and the experimentally measured data of as-synthesized AlB$_{2}$-type tantalum diborides with the claimed composition of TaB$_{\thicksim2}$, available in the literature, suggests that, instead of being a line compound with a stoichiometric composition of TaB$_{2}$, AlB$_{2}$-type tantalum diboride is readily boron-deficient, and its stable composition in equilibrium may be ranging at least from TaB$_{\thicksim1.833}$ to TaB$_{\thicksim1.75}$. Furthermore, the substitution of vacancies for boron atoms in $\alpha$$-$TaB$_{2}$ is responsible for destabilization of WB$_{2}$-type tantalum diboride and orthorhombic Ta$_{2}$B$_{3}$, predicted in the previous theoretical studies to be thermodynamically stable in the Ta$-$B system, and it thus enables the interpretation of why the two compounds have never been realized in actual experiments.

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Section: Cluster-expansion Methodsmentioning

confidence: 99%

Section: In Search Of Ground-state Structures Of α−Tab 2−xmentioning

confidence: 99%

Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB₂-type tantalum diborides as revealed by first-principles calculations

Ektarawong

Johansson²,

Pakornchote

et al. 2023

J. Phys. Mater.

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“…Out of these, the antisite and interstitial defects in MB 2 are found to be energetically unfavourable. [15,27] In fact, our preliminary phonon calculations for B Zr antisites show dynamical instability (see ESI). Metal and boron vacancies, on the other hand, have been reported to be present in some concentrations in MB 2 .…”

Section: Effect Of Vacanciesmentioning

confidence: 81%

“…Metal and boron vacancies, on the other hand, have been reported to be present in some concentrations in MB 2 . [26,27,[50][51][52][53] Defects change the local environment of charge distribution, mass density, chemical bonding which are static properties but affect the forces seen by dynamic properties. Vacancy defects exhibit their effect through change in these properties only and hence are phenomenologically treated like any other point defect.…”

Section: Effect Of Vacanciesmentioning

confidence: 99%

Site independent strong phonon-vacancy scattering in high temperature ceramics ZrB$_2$ and HfB$_2$

Sonar¹,

Dehankar²,

Vijayalakshmi³

et al. 2022

Preprint

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Similar effects of metal and boron vacancies on phonon scattering and lattice thermal conductivity (κ l ) of ZrB2 and HfB2 are reported. These defects challenge the conventional understanding that associates larger impacts to bigger defects. We find the underlying reason to be a strong local perturbation caused by the boron vacancy that substantially changes the interatomic force constants. In contrast, a long ranged but weaker perturbation is seen in the case metal vacancies. We show that these behaviours originate from a mixed metallic and covalent bonding nature in the metal diborides. The thermal transport calculations are performed in a complete ab initio framework based on Boltzmann transport equation and density functional theory. Phonon-vacancy scattering is calculated using ab initio Green's function approach. Effects of natural isotopes and grain boundaries on κ l are also systematically investigated, however we find an influential role of vacancies to explain large variations seen in the experiments. We further report a two-order of magnitude difference between the amorphous and pure-crystal limits. Our results outline significant material design aspects for these multi-functional high temperature ceramics.

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“…Apart from the double-metal diborides, such a band-filling scenario has theoretically been found to play a crucial role in determining the thermodynamic stability and mechanical properties of some single-metal diborides − for example, AlB 17 and TaB 18 , 19 . In the case of TaB , the effect of band filling can be triggered by partial substitution of vacancies for B atoms in the diboride.…”

Section: Introductionmentioning

confidence: 99%

First-principles demonstration of band filling-induced significant improvement in thermodynamic stability and mechanical properties of Sc$$_{1-x}$$Ta$$_{x}$$B$$_{2}$$ solid solutions

Mopoung

Ektarawong

Bovornratanaraks

et al. 2023

Sci Rep

Self Cite

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Mixtures of different metal diborides in the form of solid solutions are promising materials for hard-coating applications. Herein, we study the mixing thermodynamics and the mechanical properties of AlB$$_{2}$$ 2 -structured Sc$$_{1-x}$$ 1 - x Ta$$_{x}$$ x B$$_{2}$$ 2 solid solutions using the first-principles method, based on the density functional theory, and the cluster-expansion formalism. Our thermodynamic investigation reveals that the two diborides readily mix with one another to form a continuous series of stable solid solutions in the pseudo-binary TaB$$_{2}$$ 2 $$-$$ - ScB$$_{2}$$ 2 system even at absolute zero. Interestingly, the elastic moduli as well as the hardness of the solid solutions show significant positive deviations from the linear Vegard’s rule evaluated between those of ScB$$_{2}$$ 2 and TaB$$_{2}$$ 2 . In case of Sc$$_{1-x}$$ 1 - x Ta$$_{x}$$ x B$$_{2}$$ 2 , the degrees of deviation from such linear trends can be as large as 25, 20, and 40% for the shear modulus, the Young’s modulus, and the hardness, respectively. The improvement in the stability as well as the mechanical properties of Sc$$_{1-x}$$ 1 - x Ta$$_{x}$$ x B$$_{2}$$ 2 solid solutions relative to their constituent compounds is found to be related to the effect of electronic band filling, induced upon mixing TaB$$_{2}$$ 2 with ScB$$_{2}$$ 2 . These findings not only demonstrate the prominent role of band filling in enhancing the stability and the mechanical properties of Sc$$_{1-x}$$ 1 - x Ta$$_{x}$$ x B$$_{2}$$ 2 , but also it can potentially open up a possibility for designing stable/metastable metal diboride-based solid solutions with superior and widely tunable mechanical properties for hard-coating applications.

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Coupling of lattice dynamics and configurational disorder in metal deficient Al1−δB2 from first-principles

Abstract: The quantum confinement effect on the spectrum of near-field thermal radiation by quantum dots

Cited by 10 publications

References 53 publications

Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB₂-type tantalum diborides as revealed by first-principles calculations

Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB₂-type tantalum diborides as revealed by first-principles calculations

Site independent strong phonon-vacancy scattering in high temperature ceramics ZrB$_2$ and HfB$_2$

First-principles demonstration of band filling-induced significant improvement in thermodynamic stability and mechanical properties of Sc$$_{1-x}$$Ta$$_{x}$$B$$_{2}$$ solid solutions

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Coupling of lattice dynamics and configurational disorder in metal deficient Al1−δB2 from first-principles

Abstract: The quantum confinement effect on the spectrum of near-field thermal radiation by quantum dots

Cited by 10 publications

References 53 publications

Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB2-type tantalum diborides as revealed by first-principles calculations

Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB2-type tantalum diborides as revealed by first-principles calculations

Site independent strong phonon-vacancy scattering in high temperature ceramics ZrB$_2$ and HfB$_2$

First-principles demonstration of band filling-induced significant improvement in thermodynamic stability and mechanical properties of Sc$$_{1-x}$$Ta$$_{x}$$B$$_{2}$$ solid solutions

Contact Info

Product

Resources

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Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB₂-type tantalum diborides as revealed by first-principles calculations

Boron vacancy-driven thermodynamic stabilization and improved mechanical properties of AlB₂-type tantalum diborides as revealed by first-principles calculations