Surface Science of Complex Metallic Alloys

Fournée, V.; Ledieu, J.; Park, Jeong Young

doi:10.1002/9783527632718.ch4

Cited by 4 publications

(7 citation statements)

References 155 publications

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“…(Here 'closely related' means, for instance, that surface deviations from bulk structure consist of missing atoms, or relaxed interlayer spacings.) The terminations are usually dense planes that are rich in the component having lowest elemental surface energy [43]. On the basis of the bulk structure of Gd 5 Ge 4 and our DFT calculations, the possible (001) terminations are pure Gd (Gd 1 and Gd 2 ), pure Ge (Ge 2+3 ), and a mixed composition (Gd-Ge 1 ).…”

Section: Discussionmentioning

confidence: 90%

Structure of the clean Gd₅Ge₄(010) surface

Yuen¹,

Miller²,

Lei³

et al. 2013

J. Phys.: Condens. Matter

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We have characterized the (010) surface of Gd5Ge4 using scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy. Data from different samples have the following features in common: (1) the surface composition equals the bulk composition to within 5 at.%, both after ion etching and after annealing at temperatures of 400-1200 K; and (2) the surface exhibits terraces of two types. The height of the steps between similar terraces corresponds well to the separation between equivalent layers along the h010i direction in the bulk structure. Density functional theory (DFT) shows that the surface energy of the (0001) plane of hexagonal close-packed Gd is lower than that of the (111) plane of diamond-type Ge, suggesting that surfaces of Gd5Ge4 (for comparable density) should be rich in Gd. Indeed, DFT shows that among the bulk terminations of Gd5Ge4, a pure Ge termination is not favored. Each of the three remaining terminations (two pure Gd and one mixed, Gd-Ge) has its minimum surface energy in a different range of the possible Gd chemical potentials, indicating that different terminations may be stable under different conditions. DFT shows that the heights of the steps between dissimilar terraces, measured in STM, are consistent with the two pure Gd terminations. Abstract.We have characterized the (010) surface of Gd5Ge4 using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy. Data from different samples have the following features in common: (1) Surface composition equals bulk composition to within 5 atomic %, both after ion etching and after annealing at temperatures of 400 K to 1200 K; and (2) The surface exhibits two types of terraces.Step heights between similar terraces correspond well to the separation between equivalent layers along the <010> direction in the bulk structure. Density functional theory (DFT) shows that the surface energy of the (0001) plane of hcp Gd is lower than that of the (111) plane of diamond-type Ge, suggesting that surfaces of Gd5Ge4 (for comparable density) should be Gd-rich. Indeed, among the bulk terminations of Gd5Ge4, DFT shows that a pure Ge termination is not favored. The three remaining terminations (two pure Gd and one mixed DFT shows that step heights between dissimilar terraces, measured in STM, are consistent with the two pure Gd terminations.

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Section: Discussionmentioning

confidence: 90%

Structure of the clean Gd₅Ge₄(010) surface

Yuen¹,

Miller²,

Lei³

et al. 2013

J. Phys.: Condens. Matter

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“…The reduction reaction takes place at cathode (cathodic reaction site). The relative sizes and locations of cathodic and anodic sites are important The surface structure of SCIPs is significantly less understood compared to bulk [60,61]. Preliminary results show that the adsorption of small, covalently bonding molecules on icosahedral quasicrystals is very similar to that of pure Al substrate.…”

Section: Overview Of Electrochemical Corrosionmentioning

confidence: 98%

“…Materials 2021, 14, 5418 6 of 29 symmetry, but there are indications of five-fold symmetry related to the icosahedral arrangement of atoms in clusters [10,11,[52][53][54][55][56][57][58][59]. The surface structure of SCIPs is significantly less understood compared to bulk [60,61]. Preliminary results show that the adsorption of small, covalently bonding molecules on icosahedral quasicrystals is very similar to that of pure Al substrate.…”

Section: Crystal Structure Of Quasicrystals and Their Approximantsmentioning

confidence: 99%

“…The surface structure of SCIPs is significantly less understood compared to bulk [ 60 , 61 ]. Preliminary results show that the adsorption of small, covalently bonding molecules on icosahedral quasicrystals is very similar to that of pure Al substrate.…”

Section: Crystal Structure Of Quasicrystals and Their Approximantsmentioning

confidence: 99%

“…The termination planes are characterized by high atomic density and include elements with the lowest surface energy. Nevertheless, the interpretation of individual STM images is challenging and often needs to be accompanied by theoretical models of the surface [61]. Therefore, ab initio density functional theory (DFT) calculations have been utilized to model quasicrystalline surfaces [65,66].…”

Section: Crystal Structure Of Quasicrystals and Their Approximantsmentioning

confidence: 99%

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Aqueous Corrosion of Aluminum-Transition Metal Alloys Composed of Structurally Complex Phases: A Review

et al. 2021

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Complex metallic alloys (CMAs) are materials composed of structurally complex intermetallic phases (SCIPs). The SCIPs consist of large unit cells containing hundreds or even thousands of atoms. Well-defined atomic clusters are found in their structure, typically of icosahedral point group symmetry. In SCIPs, a long-range order is observed. Aluminum-based CMAs contain approximately 70 at.% Al. In this paper, the corrosion behavior of bulk Al-based CMAs is reviewed. The Al–TM alloys (TM = transition metal) have been sorted according to their chemical composition. The alloys tend to passivate because of high Al concentration. The Al–Cr alloys, for example, can form protective passive layers of considerable thickness in different electrolytes. In halide-containing solutions, however, the alloys are prone to pitting corrosion. The electrochemical activity of aluminum-transition metal SCIPs is primarily determined by electrode potential of the alloying element(s). Galvanic microcells form between different SCIPs which may further accelerate the localized corrosion attack. The electrochemical nobility of individual SCIPs increases with increasing concentration of noble elements. The SCIPs with electrochemically active elements tend to dissolve in contact with nobler particles. The SCIPs with noble metals are prone to selective de-alloying (de–aluminification) and their electrochemical activity may change over time as a result of de-alloying. The metal composition of the SCIPs has a primary influence on their corrosion properties. The structural complexity is secondary and becomes important when phases with similar chemical composition, but different crystal structure, come into close physical contact.

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