Surface composition of ordered alloys:  An off-stoichiometric effect

Ruban, Andrei V.

doi:10.1103/physrevb.65.174201

Cited by 31 publications

(26 citation statements)

References 14 publications

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“…As has been shown in Ref. [19] the chemical potential of an ordered alloy becomes discontinuous at the stoichiometric composition at T 0, where actually there exist two different values of the chemical potentials, whose difference is equal to the formation energy of the exchange antisite defect when two different partial antisites are created simultaneously. In the case of L1 0 ordered alloy it is equal to 8E ord , where E ord is the ordering energy, which in NiPt at T 0 K is about 0.1 Ry.…”

Section: P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 87%

“…Correspondingly it may also have great impact on the surface segregation [19]. By means of ab initio simulations, we show in the present paper that the so-called off-stoichiometric effect [19] can take place in a real system, and we investigate the temperature dependence of the surface concentration profiles below and above the bulk order-disorder phase transition.…”

mentioning

confidence: 98%

“…Although such a jump has no consequences for the point defect structures of the ordered alloys at a fixed alloy composition (which is the usual experimental situation) [16], it becomes important in the case of extended defects such as dislocations and surfaces, where the bulk defect structure may dramatically affect, for instance, the dislocation dissociation reaction [17] or initial stages of the surface oxidation [18]. Correspondingly it may also have great impact on the surface segregation [19]. By means of ab initio simulations, we show in the present paper that the so-called off-stoichiometric effect [19] can take place in a real system, and we investigate the temperature dependence of the surface concentration profiles below and above the bulk order-disorder phase transition.…”

mentioning

confidence: 99%

“…Such a qualitative transition in the segregation behavior due to a small change of the bulk alloy composition near the stoichiometric value is the so-called off-stoichiometric effect [19] which is connected to the formation of the antisite defects in the alloy due to deviations from the stoichiometric composition. In the case of Pt-rich off-stoichiometric alloys the excess of Pt atoms should appear on the Ni sublattice, thus an addition of a Pt atom to the alloy leads to the creation of a new partial Pt antisite defect on the Ni sublattice.…”

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confidence: 99%

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Antisite-Defect-Induced Surface Segregation in Ordered NiPt Alloy

et al. 2003

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Section: P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 87%

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confidence: 98%

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confidence: 99%

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confidence: 99%

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Antisite-Defect-Induced Surface Segregation in Ordered NiPt Alloy

et al. 2003

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“…In other multicomponent systems, there is evidence that even slight differences in bulk composition and/or bulk defect density can shift the chemical potential within the allowed limits and stabilize different surface structures [46,47].…”

Section: Discussionmentioning

confidence: 99%

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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