A comparison between available experimental information and the predictions of density-functional and density-functional+U approaches is presented for oxide ultrathin films grown on single-crystal metal surfaces. Prototypical examples of monolayer phases of an ionic oxide (ZnO), a late transition metal oxide (NiO), and an early transition metal oxide (TiO(2)) are considered. The aim is to validate the theoretical approaches, focusing on the prediction of structural features and the reproduction of scanning tunneling microscopy images, rationalized in terms of the local density of states of the systems. It is found that it is possible to reasonably estimate the optimal lattice constant of ultrathin supported films and that the inclusion of the Hubbard U term appreciably improves the accuracy of theoretical predictions, especially in the case of nonpolar ultrathin phases of a transition metal oxide. Moreover, the optimal value of U for the oxide layer at the interface with the metal support is found to differ from that appropriate for the bulk oxide, as a consequence of the intermixing of oxide and support electronic states and screening effects.

Due to an error in the program, we note that the plaquette values recorded in Fig. 2 of our paper have been mislabeled. The y-t plaquettes should be the x-t plaquettes, the x-t the x-y plaquettes, and the x-y the y-t plaquettes.While the relabeled results still show clear signs of vacuum polarization as described in the orginal paper, the claim there that the disparity between x-t and y-t plaquettes was negligible is now clearly questionable. Our conclusion that the simulated model matches the full model described by ͑5͒, which is manifestly symmetric under exchange of x and y, can no longer be supported. A further simulation of the model described by ͑5͒, which will require the use of an inexact algorithm, will be necessary to fully clarify the situation.However, no other aspects of our results are altered as a consequence of this error. It should be noted that the simulated model is a valid and interesting theory in its own right, and anisotropy structures similar to the one it possesses may be applicable to a number of condensed matter systems, 1,2 which suggests that field theories with a fermion sector of this form may be worth further investigation.

We present results from a Monte Carlo simulation of non-compact lattice QED in 3 dimensions in which an explicit anisotropy κ between x and y hopping terms has been introduced into the action. Using a parameter set corresponding to broken chiral symmetry in the isotropic limit κ = 1, we study the chiral condensate on 16 3 , 20 3 , and 24 3 lattices as κ is varied, and fit the data to an equation of state which incorporates anisotropic volume corrections. The value κ c at which chiral symmetry is apparently restored is strongly volume-dependent, suggesting that the transition may be a crossover rather than a true phase transition. In addition we present results on 16 3 lattices for the scalar meson propagator, and for the Landau gauge-fixed fermion propagator. The scalar mass approaches the pion mass at large κ, consistent with chiral symmetry restoration, but the fermion remains massive at all values of κ studied, suggesting that strong infra-red fluctuations persist into the chirally symmetric regime. Implications for models of high-T c superconductivity based on anisotropic QED 3 are discussed.

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Theoretical calculations of the work function of monolayer (ML) and bilayer (BL) oxide films on the Ag(100) surface are reported and analyzed as a function of the nature of the oxide for first-row transition metals. The contributions due to charge compression, charge transfer and rumpling are singled out. It is found that the presence of empty d-orbitals in the oxide metal can entail a charge flow from the Ag(100) surface to the oxide film which counteracts the decrease in the work function due to charge compression. This flow can also depend on the thickness of the film and be reduced in passing from ML to BL systems. A regular trend is observed along first-row transition metals, exhibiting a maximum for CuO, in which the charge flow to the oxide is so strong as to reverse the direction of rumpling. A simple protocol to estimate separately the contribution due to charge compression is discussed, and the difference between the work function of the bare metal surface and a Pauling-like electronegativity of the free oxide slabs is used as a descriptor quantity to predict the direction of charge transfer.