No abstract

Un calcul des états électroniques d de VO2 à partir des premiers principes a été effectué. On utilise, de manière auto-cohérente, la méthode par diffusion multiple, avec traitement statistique de l'échange. Un octaèdre VO86a été utilisé pour représenter la phase tétragonale et un amas V2O12-10 avec des atomes de vanadium appariés a été utilisé pour la phase monoclinique. Les résultats obtenus sont en contradiction avec une explication de l'origine de la bande interdite du semiconducteur en terme de séparation de bandes induite par la distorsion. Abstract.-An ab-initio cluster calculation of the electronic d-states in VO2 has been made by using the self-consistent statistical exchange multiple scattering method. A VO8-6 octaedron was used to represent the tetragonal phase, and a V2O12-10 cluster with paired vanadium atoms was used for the monoclinic phase. Our results are in conflict with an explanation of the semiconducting gap in terms of simple distortion-induced band splitting.

Herein we explore whether the social psychology theory of commitment via a truth-telling oath can reduce coordination failure. Using a classic sequential coordination game, we ask all players to sign voluntarily a truth-telling oath before playing the game with cheap-talk communication.Three results emerge with commitment-via-the-oath: (1) coordination increased by nearly 50 percent; (2) senders' messages were significantly more truthful and actions more efficient, and (3) receivers' trust of messages increased.

We offer a novel investigation of the effect of environmental risk on cooperation in the Voluntary Contribution Mechanism. Our baseline is the standard setting, in which the personal return from the public good is deterministic, homogeneous, and publicly known. Our experimental treatments alter this classic design by making the marginal per capita return from the public good probabilistic. In the homogeneous risk (HomR) treatment, the random draw is made for the whole group, whereas in the heterogeneous risk (HetR) treatment, this happens independently for each group member. Our hypothesis is that different environmental risks may differently affect the ex post payoff inequalities, so that other‐regarding preferences (inequality aversion) may generate higher contributions in HomR than in HetR. Our main result is that the environmental risk does not affect the patterns of cooperation either in the one‐shot or in the finitely repeated version of the game. This suggests that the standard experimental methodology provides a robust and conservative measure of human cooperation.