Abstract by: Guido Fratesi

Quantum and Classical Image Charges at Metal Surfaces

Point charges at a metal surface are balanced by image charges canceling their electrostatic potential below the surface. This well-known phenomenon is at the basis of important observations also at the nanometer length scale, where a quantum description proves essential, but may escape common first-principle theoretical approaches.

By reviewing two different examples, I will discuss cases where standard description by Density Functional Theory with the independent-particle Kohn-Sham formalism (KS-DFT) can / cannot grasp the true findings. (i) The potential for an electron at a jellium surface in common uses of KS-DFT dramatically misses the correct decay at large distances, which is due to coupling with dynamical fluctuations in the surface charge density, and is restored by higher level of theory explicitly including electron-electron many-body interactions [1-3]. (ii) An alkali atom adsorbed on a metal typically charges positively, resulting in a strong dipole whose electric field below the surface is balanced by image dipole. The occurrence of the image dipole affects the interaction between the adsorbates, the charge transfer and magnitude of the dipole itself, aspects that we show to be described by KS-DFT calculations [4-9] well validated by the quantitative agreement to a variety of experimental findings [10,6,8].

References:

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[7] G. Fratesi, A. Pace, and G.P. Brivio, J. Phys.-Condens. Matter 22, 304005 (2010), DOI: http://dx.doi.org/10.1088/0953-8984/22/30/304005

[8] C. Huang, G. Fratesi, D.A. MacLaren, W. Luo, G.P. Brivio, and W. Allison, Phys. Rev. B 82, 081413(R) (2010), DOI: http://dx.doi.org/10.1103/PhysRevB.82.081413

[9] G. Fratesi, Phys. Rev. B 84, 155424 (2011), DOI: http://dx.doi.org/10.1103/PhysRevB.84.155424

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