Abstract. Using the newly developed VASP2WANNIER90 interface we have constructed maximally localized Wannier functions (MLWFs) for the e g states of MLWFs in LaMnO 3 using PBE, PBE+U, HSE and GW 0 2 the prototypical Jahn-Teller magnetic perovskite LaMnO 3 at different levels of approximation for the exchange-correlation kernel. These include conventional density functional theory (DFT) with and without additional on-site Hubbard U term, hybrid-DFT, and partially self-consistent GW. By suitably mapping the MLWFs onto an effective e g tight-binding (TB) Hamiltonian we have computed a complete set of TB parameters which should serve as guidance for more elaborate treatments of correlation effects in effective Hamiltonian-based approaches. The method-dependent changes of the calculated TB parameters and their interplay with the electron-electron (el-el) interaction term are discussed and interpreted. We discuss two alternative model parameterizations: one in which the effects of the el-el interaction are implicitly incorporated in the otherwise "noninteracting" TB parameters, and a second where we include an explicit mean-field el-el interaction term in the TB Hamiltonian. Both models yield a set of tabulated TB parameters which provide the band dispersion in excellent agreement with the underlying ab initio and MLWF bands.

The activation of CO 2 is one of the most important topics in catalysis.[1] For example, one of the simple Zn-enzymecatalyzed processes, the hydration of CO 2 by carbonic anhydrase, has led to extensive mechanistic and theoretical studies of the interaction of CO 2 with Zn-OH. [2][3][4][5] Also, in heterogeneous catalysis, a detailed understanding of the surface chemistry of CO 2 is an important issue; interest in this topic ranges from developing new processes for an emplacement of this greenhouse gas to the synthesis of methanol from syngas (CO/CO 2 /H 2 ) over Cu/ZnO catalysts. [6] Numerous studies have been reported on CO 2 adsorption on clean metal surfaces, where frequently activation is found to occur via the formation of a bent CO 2 dÀ species. [7][8][9] For oxide surfaces much less information is available. This deficit is in part due to the poor electric conductivity of many oxides which severely complicates the application of electron-based spectroscopic methods. In particular, there is a lack of information concerning molecular vibrations from highresolution electron energy loss spectroscopy (HREELS).The application of HREELS on oxide surfaces is-in addition to the electric conductivity problem-severely limited by the presence of intense substrate lattice excitations (FuchsKliewer phonons [10] ) which obscure the relatively weak vibrational modes of adsorbed species.Herein we present the results of a systematic multitechnique experimental and theoretical study on the interaction of CO 2 with the mixed-terminated ZnO(101 0) surface. In contrast to other oxides, ZnO is sufficiently conductive that electron-based methods can be applied without significant difficulties. The results from HREELS, thermal desorption spectroscopy (TDS), low-energy electron diffraction (LEED), He-atom scattering (HAS), and X-ray photoelectron spectroscopy (XPS) reveal a complicated scenario, comprising the presence of two different ordered phases. By employing accurate periodic density-functional theory (DFT) and wave-function-based quantum-chemical cluster calculations it could be shown that the previously proposed bidentate bonding of CO 2 to this ZnO surface [11] has to be revised. Exposure to CO 2 leads-even at temperatures below 100 Kto the formation of an unusual tridentate carbonate species with the two O atoms of the CO 2 molecule being almost equivalently bound to two different Zn surface atoms.In a first set of experiments, the phase diagram of CO 2 adlayers on this ZnO substrate was determined using HAS. This technique uses neutral He atoms with thermal energy so charging problems are avoided. HAS is a highly sensitive surface-analysis method, [12][13][14] and has been successfully used to determine the phase diagram of H 2 O on the same surface.[15] The HAS data show that exposure of the sample to very small amounts of CO 2 in two steps (first with 4 L at 260 K and then 8 L at 120 K; exposures are given in units of langmuir (1 L = 1.33 10 À6 mbar s)) results in the formation of a well-ordered (2 1) phase (Figure 1 ...

Maximally localized Wannier functions (MLWFs) based on Kohn-Sham band-structures provide a systematic way to construct realistic, materials specific tight-binding models for further theoretical analysis. Here, we construct MLWFs for the Mn eg bands in LaMnO3, and we monitor changes in the MLWF matrix elements induced by different magnetic configurations and structural distortions. From this we obtain values for the local Jahn-Teller and Hund's rule coupling strength, the hopping amplitudes between all nearest and further neighbors, and the corresponding reduction due to the GdFeO3-type distortion. By comparing our results with commonly used model Hamiltonians for manganites, where electrons can hop between two "eg-like" orbitals located on each Mn site, we find that the most crucial limitation of such models stems from neglecting changes in the underlying Mn(d)-O(p) hybridization.

The fundamental aspects of spin-dependent transport processes and their interplay with temperature gradients, as given by the spin Seebeck coefficient, are still largely unexplored and a multitude of contributing factors must be considered. We used density functional theory together with a Monte-Carlo-based statistical method to simulate simple nanostructures, such as Co nanowires and films embedded in a Cu host or in vacuum, and investigated the influence of spin-disorder scattering on electron transport at elevated temperatures. While we show that the spin-dependent scattering of electrons due to temperature induced disorder of the local magnetic moments contributes significantly to the resistance, thermoelectric and spin-caloric transport coefficients, we also conclude that the actual magnitude of these effects cannot be predicted, quantitatively or qualitatively, without such detailed calculations.

Not what you'd expect: Contrary to what is usually believed for oxide surfaces, density functional calculations show that not F centers but missing ZnO dimers are the thermodynamically most favorable type of atomic defect on the nonpolar ZnO surface. Simulated STM data may serve as a fingerprint for experimental identification of the different surface defect types. The picture shows a tunneling tip over ZnO (Zn gray, O red, W blue) with the corresponding STM image in between.