Calculation of the surface energy of hcp-metals with the empirical electron theory

Fu, Baoqin; Liu, Wei; Li, Zhilin

doi:10.1016/j.apsusc.2009.07.034

Cited by 131 publications

(56 citation statements)

References 40 publications

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“…This range is higher 160 than the 12 − 16% range of FCC metals [18], suggesting the surface energy of HCP metals are generally more anisotropic. This comparatively higher anisotropy in HCP metals is also reported from some other computational methods [25,26,9], but the 15 − 21% range calculated in this work is much lower than a typical > 30% range suggested in other theoretical works. presented in all figures.…”

contrasting

confidence: 37%

“…Although works on this 140 aspect for HCP metals are limited, the quantitative difference between relaxed and unrelaxed surface energy for cubic metals is widely accepted to be orientation-dependent. The degree of this anisotropy is found to vary from [25] e equivalent crystal theory (ECT). Ref.…”

Section: Resultsmentioning

confidence: 99%

“…It can be seen that our calculated results generally agree with the extrapolated measurements, with major discrepancies occur on the three divalent sp met-als, namely Mg, Zn and Cd, where our results are substantially lower. It is noteworthy that such disagreement is also shared by other geometry based approaches [6,25], so it would seem broken-bond type models can not describe the behaviours of these metals. The overall strength of anisotropy, γ max /γ min − 1, is of the 15 − 21% range in our results.…”

mentioning

confidence: 93%

“…However, the computational costs of these methods raise dramatically for atomically complex surfaces and thus render them less suitable for the investigation of the full anisotropy of surface energy. Being regarded as brittle materials thus overlooked in the past, hexagonal 25 close-packed (HCP) metals attract a recent resurgence of interests owing to some of the unique properties they possess. Nonetheless, compared to cubic metals, the knowledge regarding HCP metals in the context of surface energy, particularly its anisotropy, is somewhat limited.…”

Section: Introductionmentioning

confidence: 99%

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Surface energy and its anisotropy of hexagonal close-packed metals

Luo

Qin

2014

Surface Science

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The absolute unrelaxed surface energy and its full orientation-dependent behaviour of 13 HCP metals are studied via a broken-bond base geometric model. The model is integrated with the Rose-Vinet universal potential to investigate arbitrary orientations which are not assessable by other methods. Using only three materials constants, the calculated results show only marginal discrepancies with reported experimental values, except for divalent sp metals Mg, Zn and Cd where the calculated values are lower by a factor of 2. Stereographic projections of all 13 metals show global minimum on (0001) pole with an overall anisotropy of 15% to 21%. The equilibrium crystal shape of HCP is found to be truncated hexagonal bi-prismatic, with (0001) always favoured but the bi-prismatic facets vary from one metal to another. All projection patterns show strong six-fold symmetries but are unique for every element. The patterns are found to be largely determined by an anharmonicity factor η. Best agreement with experimental findings are found for Be, Sc, Ti,Y, Zr and Hf which possess comparatively low η. We believe the stereographic projections of these elements are the more representative for HCP metals.

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confidence: 37%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Surface energy and its anisotropy of hexagonal close-packed metals

Luo

Qin

2014

Surface Science

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“…32 Closely packed planes have higher binding energy and, thus, lower surface energy. The theoretically calculated surface energies of Mg (0001), and (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) 33 A higher surface energy can result in an increased dissolution rate. The theoretical dissolution rates of Mg crystallographic planes (10-10) and (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) are predicted to be about 18-20 times higher than that of the basal plane (0001).…”

Section: Discussionmentioning

confidence: 99%

Corrosion Behavior of Pure Magnesium with Low Iron Content in 3.5 wt% NaCl Solution

Yang

Zhou

Curioni

et al. 2015

J. Electrochem. Soc.

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The microstructure and corrosion behavior of pure magnesium, with 25 ppm Fe but a high corrosion rate, have been studied in this work. It was found that Fe-rich particles, containing also Si, distribute non-uniformly in the Mg matrix and they are spaced at a distance of 100-1000 μm. Before the initiation of localized corrosion, Fe-rich particles play a key role in determining the overall corrosion behavior by supporting hydrogen evolution. During corrosion propagation, Fe-rich particles could be oxidized once they were detached from the Mg matrix and, consequently, lose their cathodic activation. Once the corrosion has taken place over majority of the surface, the effects of crystallographic orientation of the underlying metal dominate the last stage of corrosion, which propagates parallel to the (0001) Magnesium alloys are of great value for industrial applications due to their low density and high strength-to-weight ratio. However, a major deficiency is their comparatively poor corrosion resistance when exposed to aqueous and humid environments.1,2 Consequently, there is a demand to develop magnesium alloys with improved corrosion resistance. 2,3The equilibrium potential for magnesium oxidation is well below the equilibrium potential for hydrogen evolution over the entire pH range of practical interest. As a consequence, the cathodic reaction of hydrogen evolution largely dominates over oxygen reduction during corrosion in an aqueous environment. For this reason, the presence of elements with low overpotentials (or high exchange current density) for hydrogen evolution is likely to produce detrimental effects on the corrosion resistance due to increase in the hydrogen evolution rate. Hanawalt et al. 4 found that four elements (Fe, Ni, Cu, and Co) had a very profound effect on accelerating the corrosion rate of Mg in chloride-containing aqueous environments even at concentrations below 0.2 wt%. Subsequent studies have confirmed that the most critical factor affecting the corrosion behavior of Mg is the presence of impurities.3

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Functionalized Zn@ZnO Hexagonal Pyramid Array for Dendrite‐Free and Ultrastable Zinc Metal Anodes

Kim

Liu

Shim

et al. 2020

Adv Funct Materials

173

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Here, an electrode comprising a Zn hexagonal pyramid array (HPA) coated with a functionalized ZnO layer (Zn@ZnO HPA) is prepared using a periodic anodizing technique. The HPA structure markedly increases the electroactive surface area of Zn anode, thus decreasing the local current density. Furthermore, the functionalized ZnO coating layer has a gradient thickness that plays an important role in the selective deposition of Zn ions and the mitigation of side reactions at the interface. The electrochemical stability of the Zn@ZnO HPA electrode, which is closely related to the electroactive surface area and charge transfer resistance, is determined by the “split” value, i.e., ratio of current‐off to current‐on time, a parameter of the periodic anodizing process. Compared with the pristine Zn‐based symmetric cell, the Zn@ZnO HPA‐based symmetric cell is safely operated in the investigated experimental range with the 10‐fold improved running life and 25‐fold enhanced current density without Zn dendrite growth. Moreover, the Zn@ZnO HPA/MnO2 battery exhibits outstanding long‐term cyclability (nearly 100%) with greater than 99% Coulombic efficiency after 1000 cycles at a current density of 9 A g−1. This periodic anodizing technique for ultrastable Zn metal anodes is expected to contribute to the development of inherently safe energy storage systems.

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Calculation of the surface energy of hcp-metals with the empirical electron theory

Cited by 131 publications

References 40 publications

Surface energy and its anisotropy of hexagonal close-packed metals

Surface energy and its anisotropy of hexagonal close-packed metals

Corrosion Behavior of Pure Magnesium with Low Iron Content in 3.5 wt% NaCl Solution

Functionalized Zn@ZnO Hexagonal Pyramid Array for Dendrite‐Free and Ultrastable Zinc Metal Anodes

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