A comparative analysis of the mechanisms of ammonia synthesis on various catalysts using density functional theory

In this review, we present the recent progress in ammonia synthesis research using density functional theory (DFT) calculations on various industrial catalysts, metal nitrides and nano-cluster-supported catalysts. The mechanism of ammonia synthesis on the industrial Fe catalyst is generally accepted to be a dissociative mechanism . We have recently found, using DFT techniques, that on Co 3 Mo 3 N (111) surfaces, an associative mechanism in the synthesis of ammonia can offer a new low-energy pathway that was previously unknown. In particular, we have shown that metal nitrides that are also known to have high activity for ammonia synthesis can readily form nitrogen vacancies which can activate dinitrogen, thereby promoting the associative mechanism. These fundamental studies suggest that a promising route to the discovery of low-temperature ammonia synthesis catalysts will be to identify systems that proceed via the associative mechanism, which is closer to the nitrogen-fixation mechanism occurring in nitrogenases.

How Associative Thinking Influences Scene Perception

Perception of our external environment is not isolated from the influence of our internal thoughts. Here, we investigate the nature of their interaction. We argue that a common associative mechanism underlies both the perception of scenes and our internal thoughts, and in three experiments hypothesize that there is a functional advantage to an associative thought pattern in the perception of scenes. Experiments 1 and 2 showed that associative thinking indeed facilitates scene perception, an effect that evolved over the course of the experiments. Experiment 3 showed that associative thinking hinders the perception of individual, isolated objects, in which associative information is minimized, but that object perception is facilitated when associative thinking is reduced. This double dissociation reveals that a match between the orientation of internal and external processing is key for perception, suggesting that an associative mind is more receptive of externally perceived associative information.

Powiązania syntagmatyczne w sieciach leksykalnych na przykładzie leksemu matka

Syntagmatic connections in lexical networks on the example of the mother lexeme Summary The article presents two lexical networks, the first of which is an experimental lexical network, which was created as a result of a cyclically conducted test on a group of 900 participants. This network uses the human associative mechanism. The second network was built using the Word-to-Vector algorithm. The syntagmatic links describe the meaning of the lexeme well. The article describes how the two networks represent the meaning of the mother lexeme. This particular example shows well the differences between sets of words obtained in different ways, i.e. with the use of the human associative mechanism – an experimental lexical network and a well-built algorithm. The experimental lexical network contains rich emotional characteristics of the mother lexeme, i.e. syntagmatic connections, which is fundamentally different from the set of words generated for the mother lexeme by the W2Vec algorithm.

A Matter of Perspective: How adults represent causal launching sequences

The ability to reason about causal events in the world is fundamental to cognition. Despite the importance of this ability, little is known about how adults represent causal events, what structure or form those representations take, and what the mechanism is that underpins such representations. We report four experiments with adults that examine the perceptual basis on which adults represent four-object launching sequences (Experiments 1 and 2), whether adults representations reflect sensitivity to the causal, perceptual, or causal and perceptual relation among the objects that comprise such sequences (Experiment 3), and whether such representations extend beyond spatiotemporal contiguity to include other low-level stimulus features such as an object’s shape and color (Experiment 4). Based on these results of the four experiments, we argue that a domain-general associative mechanism, rather a modular, domain-specific, mechanism subserves adults’ representations of four-object launching sequences.

A density functional theory study of the oxygen reduction reaction on the (111) and (100) surfaces of cobalt(II) oxide

Density functional theory calculations were employed to investigate the electrochemical oxygen reduction reaction on the (111) and (100) surfaces of cobalt(II) oxide. Different mechanisms were applied to evaluate the oxygen reduction reaction performance of cobalt(II) oxide structures in terms of the Gibbs free energy and density of states. A variety of intermediate structures based on associative and dissociative mechanisms were constructed and optimized. As a result, we estimated the catalytic activity by calculating the free energy of the intermediates and constructing free energy diagrams, which suggested that the oxygen reduction reaction Gibbs free energy on cobalt(II) oxide (111) and (100) surfaces based on the associative mechanism is smaller than that based on the dissociative mechanism, demonstrating that the associative mechanism should be more likely to be the oxygen reduction reaction pathway. Moreover, the theoretical oxygen reduction reaction activity on the cobalt(II) oxide (111) surface was found to be higher than that on the cobalt(II) oxide (100) surface. These results shed light on the rational design of high-performance cobalt(II) oxide oxygen reduction reaction catalysts.

Mechanistic insights of anionic ligand exchange and fullerene reduction with magnesium(i) compounds

Exchange of anionic ligands on the Mg22+ ion via an associative mechanism can be facile and depends on ligand sterics and shape.