The band gap problem: the accuracy of the Wien2k code confronted

This paper is a continuation of our detailed study [Phys. Rev. B 86, 195106 (2012)] of the performance of the recently proposed modified Becke-Jonhson potential (mBJLDA) within the known Wien2k code. From the 41 semiconductors that we have considered in our previous paper to compute the band gap value, we selected 27 for which we found low temperature experimental data in order to pinpoint the relative situation of the newly proposed Wien2k(mBJLDA) method as compared to other methods in the literature. We found that the GWA gives the most accurate predictions. The Wien2k (mBJLDA) code is slightly less precise, in general. The Hybrid functionals are less accurate, on the overall. The GWA is definitely the most precise existing method nowadays. In 88% of the semiconductors considered the error was less than 10%. Both, the GWA and the mBJLDA potential, reproduce the band gap of 15 of the 27 semiconductors considered with a 5% error or less. An extra factor to be taken into account is the computational cost. If one would seek for precision without taking this factor into account, the GWA is the method to use. If one would prefer to sacrifice a little the precision obtained against the savings in computational cost, the empirical mBJLDA potential seems to be the appropriate method. We include a graph that compares directly the performance of the best three methods, according to our analysis, for each of the 27 semiconductors studied. The situation is encouraging but the problem is not yet a closed issue.Comment: 8 pages, 1 figur

Interannuale Klimavariabilität im tropischen Indischen Ozean: Eine Untersuchung mit einer Hierarchie von globalen gekoppelten Ozean-Atmosphären-Modellen

The Indian Ocean shows significant climate variability at interannual timescales. This variability is affected by the El Niño--Southern Oscillation (ENSO) phenomenon. A hier-archy of coupled model simulations is used as well as observational datasets and reanaly-sis products to investigate the role ENSO plays in determining the interannual climate variability in the Indian Ocean and to investigate the spatial and temporal characteristics of the ENSO--independent climate variability. The hierarchy of coupled model simula-tions comprises three experiments. Two experiments are conducted with the ECHO-G model, which is a state--of--the--art ocean--atmosphere general circulation model (CGCM). The first experiment with ECHO-G is a standard integration, which serves as a control integration. The second experiment with ECHO-G is similar to the control ex-periment but the interannual ocean--atmosphere interactions have been inhibited in the tropical Pacific Ocean, so that in this experiment the ENSO signal is excluded by defini-tion. The third experiment is conducted with a fixed--depth mixed--layer model coupled to the same atmosphere model that has been used in the two experiments with ECHO-G. This integration allows the investigation of the role of ocean dynamics in the generation of interannual sea surface temperature (SST) variability. It is shown that the variability of several atmospheric and oceanic fields in the Indian Ocean region, including SST, is consistent with a cycle only if ENSO is included in the simulation. The ENSO signature in the Indian Ocean includes both a dynamical and a thermodynamical response. ENSO influences the Indian Ocean at two different interannual timescales and provides conditions favorable for coupled ocean-atmosphere interac-tions in the Indian Ocean. In contrast, the climate variability that is independent of ENSO shows a response of the ocean to the atmospheric forcing that is not significantly more energetic than expected from a stochastic forcing approach, thereby reflecting either a passive oceanic response or weak coupling in the ENSO independent Indian Ocean variability

On the Origin of the -4.4 eV Band in CdTe(100)"

We calculate the bulk- (infinite system), (100)-bulk-projected- and (100)-Surface-projected Green's functions using the Surface Green's Function Matching method (SGFM) and an empirical tight-binding hamiltonian with tight-binding parameters (TBP) that describe well the bulk band structure of CdTe. In particular, we analyze the band (B--4) arising at --4.4 eV from the top of the valence band at $\Gamma$ according to the results of Niles and H\"ochst and at -4.6 eV according to Gawlik {\it et al.} both obtained by Angle-resolved photoelectron spectroscopy (ARPES). We give the first theoretical description of this band.Comment: 17 pages, Rev-TEX, CIEA-Phys. 02/9