Static and dynamic displacements of nickel atoms in clean and oxygen covered Ni(001) surfaces

Frenken, J.W.M.; Smeenk, R.G.; Veen, J. F. van der

doi:10.1016/0039-6028(83)90216-9

Cited by 96 publications

(17 citation statements)

References 54 publications

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Section: (Received 24 November 1997)mentioning

confidence: 99%

“…This process causes larger thermal motion of the surface atoms and presumably enhanced anharmonicity in the interlayer potential. As the temperature is increased, this anharmonicity can lead to large anisotropic vibrations, surface roughening, and premelting [1].Early free energy calculations with pair potentials for the (100), (110), and (111) surfaces of Cu showed that anharmonicity and its effect on the equilibrium atomic positions (thermal expansion) and the vibrations around the equilibrium atomic positions (mean-square displacements) should be 2-3 times larger at the surface as compared to the bulk [2]. The first experimental evidence for enhanced thermal expansion of a crystal surface was reported for the Pb(110) surface [3] and then for Ni(100), Ag(111), and Cu(110) [4].…”

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confidence: 99%

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Anomalously Large Thermal Expansion at the (0001) Surface of Beryllium without Observable Interlayer Anharmonicity

Pohl

Cho²,

Terakura³

et al. 1998

Phys. Rev. Lett.

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We have measured a large thermal surface expansion, 6 times larger than the bulk, on Be(0001) using low-energy electron diffraction. This observation seems to be inconsistent with previous measurements reporting negligible anharmonicity in the surface phonon modes normal to the surface. Density-functional theory calculations for the thermal expansion from the minimum in the free energy within the quasiharmonic approximation agree with the experimental observations and demonstrate that the enhanced thermal expansion is caused largely by a softening of the in-plane vibrations.[ S0031-9007(98) PACS numbers: 63.20. Ry, 68.35.Bs, 68.35.Ja Thermal expansion of a crystal is a direct manifestation of the anharmonic nature of the interatomic forces in solids. For purely harmonic interatomic potentials, the mean positions of the atoms do not change even though their vibrational amplitudes increase with temperature. Thus, an expansion upon heating is intimately related to the anharmonicity of normal modes of lattice vibrations, which, in turn, are determined by the nature of binding between the different units in the lattice. When a crystal is cleaved, a surface is formed by breaking the symmetry and reducing the coordination. This process causes larger thermal motion of the surface atoms and presumably enhanced anharmonicity in the interlayer potential. As the temperature is increased, this anharmonicity can lead to large anisotropic vibrations, surface roughening, and premelting [1].Early free energy calculations with pair potentials for the (100), (110), and (111) surfaces of Cu showed that anharmonicity and its effect on the equilibrium atomic positions (thermal expansion) and the vibrations around the equilibrium atomic positions (mean-square displacements) should be 2-3 times larger at the surface as compared to the bulk [2]. The first experimental evidence for enhanced thermal expansion of a crystal surface was reported for the Pb(110) surface [3] and then for Ni(100), Ag(111), and Cu(110) [4]. The coefficients of thermal expansion were found to be 5 to 20 times larger than in the bulk, much higher than suggested by the aforementioned theory. The assumption in all of these studies was that the enhanced thermal expansion is caused by the greatly enhanced anharmonicity of vibrations perpendicular to the surface.The first quantitative measurement of surface anharmonicity was performed on Cu(110) by Baddorf and Plummer [5] using high-resolution electron energy loss spectroscopy (HREELS). In their study, the temperature dependence of the surface phonon energies and lifetimes revealed a vibrational anharmonicity for motion normal to the surface 4-5 times greater than in the bulk. Unfortunately, there are no equivalent measurements of anharmonicity for Ag(111), Ni(100), and Pb (110) to complement the thermal expansion measurements.Recently, the density-functional theory calculations by Narasimhan and Scheffler [6] and Cho and Scheffler [7] have challenged the intuitive picture of thermal expansion. They argue that ther...

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Section: (Received 24 November 1997)mentioning

confidence: 99%

mentioning

confidence: 99%

Anomalously Large Thermal Expansion at the (0001) Surface of Beryllium without Observable Interlayer Anharmonicity

Pohl

Cho²,

Terakura³

et al. 1998

Phys. Rev. Lett.

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“…[34][35][36][37][38][39][40][41] The change in the first interlayer spacing, ⌬ 12 , was also investigated both experimentally 42,43 and computationally, 39 and was found to be a few percent. In our calculations, the surface relaxations change work functions and magnetic moments only of the order of 0.1% and the spin-polarization of tunneling conductance by less than a few percent.…”

Section: A Electronic Structures Of Ni Surfacesmentioning

confidence: 99%

Spin-polarized field emission from Ni(001) and Ni(111) surfaces

Ohwaki¹,

Wortmann

Ishida

et al. 2006

Phys. Rev. B

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Results are presented of a first-principles calculation of the spin-polarized field emission from ferromagnetic Ni͑111͒ and Ni͑001͒ surfaces. The electronic structure of both surfaces exposed to an external field is determined by combining the surface-embedded Green function approach and the full-potential linearized augmented plane-wave ͑FLAPW͒ method within the local spin density approximation. We discuss the contributions of different states to the field-emission current. In particular, we show that delocalized states make similar contributions to that obtained at jellium surfaces while localized Ni d states contribute mostly through surface states and resonances. These contributions dominate in the minority spin and lead to a negative spin polarization of the emitted current.

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“…Among the available experimental techniques, ion and atom scattering have proved to be useful [2][3][4], especially since they give real space information and are, in principle, quantitative.…”

Section: Introductionmentioning

confidence: 99%

Ion beam studies of oxygen exposed Ni(100)

Alkemade¹,

Deckers²,

Habraken³

et al. 1987

Surface Science Letters

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A clean Ni(100) surface and a surface exposed to 1802, have been studied by high-energy ion scattering and nuclear reaction analysis. The structure of the clean and the exposed surfaces is studied by 750 keV He + ion scattering in combination with channeling and blocking. The results are consistent with results obtained by medium-energy ion scattering. Absolute oxygen contents are measured using the 180(p, a)lSN nuclear resonance at Ep = 1766 keV. It is found that the oxygen content of the surface for which the c(2 X 2) LEED pattern is observed, is 0.42 + 0.04 of a Ni(100) monolayer. The oxygen content of a saturated oxide layer is 2.4_+0.2 of a monolayer. Furthermore, it is concluded that the saturated oxide layer consists of stoichiometric NiO.

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Static and dynamic displacements of nickel atoms in clean and oxygen covered Ni(001) surfaces

Cited by 96 publications

References 54 publications

Anomalously Large Thermal Expansion at the (0001) Surface of Beryllium without Observable Interlayer Anharmonicity

Anomalously Large Thermal Expansion at the (0001) Surface of Beryllium without Observable Interlayer Anharmonicity

Spin-polarized field emission from Ni(001) and Ni(111) surfaces

Ion beam studies of oxygen exposed Ni(100)

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