Pressure-induced novel compounds in the Hf-O system from first-principles calculations

Zhang, Jin; Oganov, Artem R.; Li, Xinfeng; Xue, Kan‐Hao; Wang, Zhenhai; Dong, Huafeng

doi:10.1103/physrevb.92.184104

Cited by 46 publications

(45 citation statements)

References 39 publications

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“…USPEX was previously successfully applied for investigation 5 Note that this orbital lies in the plane of Te plaquette, while central part of the charge density at Au-D is spherically symmetric and, thus, this band corresponds rather to 3z 2 − r 2 orbital. of structural properties of many different materials including those based on heavy metals [28][29][30]. For AuTe2 we found that the AuAu'Te4 structure with distortions reminding the CDW still has the lowest total energy among hundreds of other structures obtained with the USPEX.…”

Section: Mechanism Of Incommensurability In Aute 2 : Negative Charge mentioning

confidence: 81%

Old puzzle of incommensurate crystal structure of calaverite AuTe ₂ and predicted stability of novel AuTe compound

Streltsov

Roizen

Ушаков

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Gold is a very inert element, which forms relatively few compounds. Among them is a unique material-mineral calaverite, [Formula: see text] Besides being the only compound in nature from which one can extract gold on an industrial scale, it is a rare example of a natural mineral with incommensurate crystal structure. Moreover, it is one of few systems based on Au, which become superconducting (at elevated pressure or doped by Pd and Pt). Using ab initio calculations we theoretically explain these unusual phenomena in the picture of negative charge-transfer energy and self-doping, with holes being largely in the Te [Formula: see text] bands. This scenario naturally explains incommensurate crystal structure of [Formula: see text], and it also suggests a possible mechanism of superconductivity. An ab initio evolutionary search for stable compounds in the Au-Te system confirms stability of [Formula: see text] and [Formula: see text] and leads to a prediction of an as yet unknown stable compound AuTe, which until now has not been synthesized.

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Section: Mechanism Of Incommensurability In Aute 2 : Negative Charge mentioning

confidence: 81%

Old puzzle of incommensurate crystal structure of calaverite AuTe ₂ and predicted stability of novel AuTe compound

Streltsov

Roizen

Ушаков

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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“…P 62m-ZrO and P 62m-HfO are formed on x-Zr and x-Hf, and exhibit interesting structures and electronic properties. 9,20 Besides, P 62m-TiO has been proven to be the ground state of titanium monoxide and it has been experimentally detected using XRD in Amano's work. 11 There is a phase transition for ZrO at 72 GPa, from the hexagonal P 62m-ZrO with fivefold coordination of oxygen atoms to an orthorhombic Pmma-ZrO structure with sixfold coordination of oxygens ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…However, hafnium possesses a closed f-electron subshell ([Xe]4f 14 5d 2 6s 2 ), while zirconium has no f-electrons ([Kr]4d 2 5s 2 ), another noticeable difference is that neutron a) absorption cross-section of hafnium is 600 times higher than that of zirconium. In our previous work, the Hf-O system at pressures up to 120 GPa was studied by first-principles calculations, 20 while a comparative investigation of the Zr-O system is presented here.…”

Section: Introductionmentioning

confidence: 99%

First-principles investigation of Zr-O compounds, their crystal structures, and mechanical properties

Zhang

Oganov

et al. 2017

Journal of Applied Physics

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First-principles evolutionary simulations are used to systematically predict stable compounds in the Zr-O system at pressures up to 120 GPa. Zr-O compounds and Hf-O compounds share many similarities, but four new phases Cmmm-Zr 3 O, R 3c-Zr 3 O 2 , Pmma-ZrO, and Fe 2 P-type ZrO 2 (P 62m) appear in the Zr-O system: the latter two phases appear in the Hf-O system at higher pressure. OII ZrO 2 (Pnma) transforms into Fe 2 P-type ZrO 2 at 102 GPa. Meanwhile, Fe 2 P-type ZrO 2 and P 62m-ZrO have similar structures based on x-Zr. However, the calculated Vickers hardness of Fe 2 P-type ZrO 2 (5.6 GPa) is inferior to that of P 62m-ZrO (14.1 GPa). The hardness of P 62m-ZrO (14.1 GPa) is lower than that of P 62m-HfO (16.1 GPa) and P 62m-TiO (16.6 GPa). On the whole, Zr-O compounds exhibit lower hardnesses and bulk moduli than Hf-O compounds. Published by AIP Publishing. [http://dx.

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“…An investigation of the full range of Hf-O binary compounds [31] by means of an evolutionary algorithm [32][33][34], which was devoted to a search for new phases stable at high pressures in order to characterize their mechanical properties, shows that P nnm-Hf 2 O, I mm2-Hf 5 O 2 , P31m-Hf 2 O, and P4m2-Hf 2 O 3 high-pressure phases become metastable at ambient pressure. P4m2-Hf 2 O 3 structure was also predicted in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…[35], where first-principles DFT calculations were employed to search for stable metallic oxygen-deficient hafnium and zirconium oxides, which may be reachable at normal conditions from monoclinic hafnia and zirconia with assistance of an applied electric field. It should be noted, however, that the mentioned theoretical structural studies [30,31,35] were performed with the generalized gradient approximation for exchange and correlation energies [36]. This approach neglects possibly strong correlation effects within the Hf d shell, which may affect the Hf-O interaction and bonding [25].…”

Section: Introductionmentioning

confidence: 99%

Routes for increasing endurance and retention in HfO2 -based resistive switching memories

Rushchanskii

Blügel

2018

Phys. Rev. Materials

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We investigate metastable and thermodynamically stable phases that can be expected to occur in electroformed filaments in resistively switching hafnia, and discuss their relevance for the switching process. To this end, we conduct a study, based on density functional theory combined with an evolutionary algorithm determining the composition-dependent (meta)stable phases in HfO x , focusing on the region 0 < x < 2. We find that oxygen vacancies in hafnia tend to form regular patterns, which leads to periodic metastable structures featuring onedimensional open channels, thus favoring ionic conductivity in the host material, i.e., oxygen migration. The band gap of such structures is systematically lowered with increasing oxygen deficiency, resulting in metallic behavior when oxygen migrates out of the channels. Moreover, we find that the solubility of oxygen in metallic Hf is very high, up to one oxygen per six metallic atoms, the concentration corresponding to a thermodynamically stable and ordered metallic compound, Hf 6 O. Therefore, thick enough metallic capping of Hf could play the role of an active electrode for hosting oxygen which migrates out of HfO 2. In combination with reversible oxygen migration in predicted suboxide phases, this should lead to robust resistive memory cells with high endurance and long retention.

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Pressure-induced novel compounds in the Hf-O system from first-principles calculations

Cited by 46 publications

References 39 publications

Old puzzle of incommensurate crystal structure of calaverite AuTe ₂ and predicted stability of novel AuTe compound

Old puzzle of incommensurate crystal structure of calaverite AuTe ₂ and predicted stability of novel AuTe compound

First-principles investigation of Zr-O compounds, their crystal structures, and mechanical properties

Routes for increasing endurance and retention in HfO2 -based resistive switching memories

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Pressure-induced novel compounds in the Hf-O system from first-principles calculations

Cited by 46 publications

References 39 publications

Old puzzle of incommensurate crystal structure of calaverite AuTe 2 and predicted stability of novel AuTe compound

Old puzzle of incommensurate crystal structure of calaverite AuTe 2 and predicted stability of novel AuTe compound

First-principles investigation of Zr-O compounds, their crystal structures, and mechanical properties

Routes for increasing endurance and retention in HfO2 -based resistive switching memories

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Old puzzle of incommensurate crystal structure of calaverite AuTe ₂ and predicted stability of novel AuTe compound

Old puzzle of incommensurate crystal structure of calaverite AuTe ₂ and predicted stability of novel AuTe compound