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

Cellular automaton supercolliders

Gliders in one-dimensional cellular automata are compact groups of non-quiescent and non-ether patterns (ether represents a periodic background) translating along automaton lattice. They are cellular-automaton analogous of localizations or quasi-local collective excitations travelling in a spatially extended non-linear medium. They can be considered as binary strings or symbols travelling along a one-dimensional ring, interacting with each other and changing their states, or symbolic values, as a result of interactions. We analyse what types of interaction occur between gliders travelling on a cellular automaton `cyclotron' and build a catalog of the most common reactions. We demonstrate that collisions between gliders emulate the basic types of interaction that occur between localizations in non-linear media: fusion, elastic collision, and soliton-like collision. Computational outcomes of a swarm of gliders circling on a one-dimensional torus are analysed via implementation of cyclic tag systems

A non-cylindrical model of development of the Hercynian belt allochthonous terranes

[Resumen] Se propone un modelo no cilíndrico para el desarrollo del Cinturón Hercínico Europeo. Los terrenos alóctonos fuertemente trasladados que forman parte de él se componen de una mezcla de unidades catazonales y ofiolíticas, así como de fragmentos del margen continental de Gondwana. La disposición de estos terrenos y sus relaciones con la paleogeografía de Gondwana, así como las estructuras que muestran, sugieren que se emplazaron de manera oblícua, en una dirección que formaba un pequeño ángulo con el margen de este continente. El alóctono podría estar ligado al desarrollo de un arco de islas o de una subplaca con forma de cuña en la parte meridional de la placa Báltica. Con posterioridad a su emplazamiento, la convergencia entre Gondwana y Laurasia, que habría incluido movimientos transcurrentes esencialmente dextros, sería responsable de la complejidad actual del orógeno.[Abstract] A case is made for a non-cylindrical development of the European Hercynian belt. Far-travelled allochthonous terranes in it consits of a mixture of units including catazonal ones, ophiolites and units derived from the continental margin of Gondwana. Considerations upon the disposition of the terranes, their relationships with the paleogeography of the Gondwana realm and the structures in them, suggest that their emplacement took place in an oblique fashion at a small angle to the margin of this continent. The proposed allochthon could be related to the development of an island arc or a wedge-like subplate in the southern part of the Baltica plate. Later, convergence between Gondwana and Laurussia, involving transcurrent, mostly dextral movements, would account for the present complexity of the belt