Analysis of a carbon dimer bound to a vacancy in iron using density functional theory and a new tight binding model

Recent density functional theory (DFT) calculations by Foerst et al. have predicted that vacancies in both low and high carbon steels have a carbon dimer bound to them. This is likely to change the thinking of metallurgists in the kinetics of the development of microstructures. While the notion of a C2 molecule bound to a vacancy in Fe will potentially assume a central importance in the atomistic modeling of steels, neither a recent tight binding (TB) model nor existing classical interatomic potentials can account for it. Here we present a new TB model for C in Fe, based on our earlier work for H in Fe, which correctly predicts the structure and energetics of the carbon dimer at a vacancy in Fe. Moreover the model is capable of dealing with both concentrated and dilute limits of carbon in both bcc-Fe and fcc-Fe as comparisons with DFT show. We use both DFT and TB to make a detailed analysis of the dimer and to come to an understanding as to what governs the choice of its curious orientation within the vacancy

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Publikacja została sfinansowana ze środków Narodowego Programu Rozwoju Humanistyki w ramach projektu nr 12H 11 0004 8

Sauts temporels et dé-placements : Le souvenir du travail dans les machines de vision de Farocki

Cet essai soutient que les films de Harun Farocki ont toujours oscillé entre les contraintes institutionnelles, d’une part, et les failles du cinéma indépendant (financé par l’État et la télévision) et des galeries d’art (commanditées), d’autre part. Cela dit, l’autorité morale et la crédibilité esthétique de ses films et de ses installations découlent d’une « critique » à double tranchant : ses oeuvres sont critiques parce que leur portée réflexive atteint même le réalisateur, et que la boucle de rétroaction (feedback) engage également l’artiste. Quiconque explore son travail/art découvre que Farocki est vraisemblablement l’un des rares réalisateurs contemporains à pouvoir contrecarrer le monde comme oeil machinique, en redonnant à l’oeil et la main, par moment, une puissance d’implication de soi et de solidarité. Conséquemment, toute l’actualité et l’urgence de l’oeuvre de Farocki tiennent dans un effort pour sauvegarder le cinéma de sa propre dialectique de mémoire et d’oubli, d’une évocation nostalgique d’une plénitude perdue et d’une auto-réflexivité moderne, en réinventant le « travail » comme « art », et l’« art » comme « travail ».The essay argues that Harun Farocki’s films have always been poised between the institutional constraints and aesthetic faultlines of (state and television-funded) independent cinema and (commissioned) gallery art. But his films’ and installations’ moral authority and aesthetic credibility come from the fact that their “critique” cuts both ways: they are critical in the sense that their gestures of reflexivity are directed also at the director himself, and that the feedback loops implicate the artist as well. As one walks through his art/works, one realizes that he may be one of the few filmmakers today capable of countering the self-surveillance of the world as machine eye, with moments that re-instate the eye and the hand as instances of self-implication and solidarity. The true topicality and urgency of Farocki’s work may thus be nothing less than an effort to rescue the cinema from its own dialectic of memory and forgetting, of nostalgic evocation of a lost plenitude and modernist self-reflexivity, by reinventing “work” as “art”, and “art” as “work”