A new potential for methylammonium lead iodide.

We present a new set of interatomic potentials for modelling methylammonium lead iodide. The potential model uses existing potentials for lead iodide and methylammonium, and new functions are fitted to enable these pre-existing potentials to be used together, while still being capable of modelling lead iodide and methylammonium iodide as separate materials. Fitting was performed using a combination of ab initio and experimental reference data. Our simulations are in agreement with experiment and reveal the short and long range ordering of the molecular cations and lead iodide octahedra

A community of practice or a working psychological group? Group dynamics in core and peripheral community participation

The concept of communities of practice (CoP) has become increasingly influential in management literature. Yet, many scholars regard the term as too homogenous and lacking in empirical support. Our study explores the Silver Academy, a project involving over 100 unemployed and self-employed managers over the age of 50, who came together with the purpose of sharing knowledge and experience in starting up their own businesses. The study shows how the Academy matches the notion of CoP including mutual relationships, shared engagement and a common consensus of membership. However, applying Bion’s (1961) theory of groups, we challenge the homogenous and consensual notion of a community of practice, illustrating how, through unconscious group processes, some group members exhibit workgroup mentality and the capacity for realistic hard work (and leadership), while others are caught in a basic-assumption mentality, prone to feelings of anxiety, guilt and depression. This is particularly so for a group that has gone through the recent trauma of unemployment

Mood and the Market: Can Press Reports of Investors’ Mood Predict Stock Prices?

We examined whether press reports on the collective mood of investors can predict changes in stock prices. We collected data on the use of emotion words in newspaper reports on traders’ affect, coded these emotion words according to their location on an affective circumplex in terms of pleasantness and activation level, and created indices of collective mood for each trading day. Then, by using time series analyses, we examined whether these mood indices, depicting investors’ emotion on a given trading day, could predict the next day’s opening price of the stock market. The strongest findings showed that activated pleasant mood predicted increases in NASDAQ prices, while activated unpleasant mood predicted decreases in NASDAQ prices. We conclude that both valence and activation levels of collective mood are important in predicting trend continuation in stock prices

Stoichiometry-dependent local instability in MAPbI3 perovskite materials and devices

Organometallic perovskite materials based on MAPbI3 achieve photovoltaic efficiencies as high as 22% for solar cells; however, the long-term stability of these perovskite materials is still a hurdle for applications. Here, we report the air and charge induced instabilities of MAPbI3 perovskite materials with different local stoichiometry using Secondary Electron Hyperspectral Imaging (SEHI). We find that individual grains which do not have the ideal ABX3 stoichiometry degrade faster than stoichiometric grains. We also observe that the degradation pathways depend on the local stoichiometry. Non-stoichiometric grains (with excess MAI) degrade from the centre of the grain and further degradation moves towards the grain boundary, whereas in stoichiometric grains degradation sets in at the grain boundary. We further use deliberately high doses of electron beam exposure to highlight the presence of local non-stoichiometry in device cross-sections of bias degraded devices which pinpoints different onset locations of degradation, depending on the local stoichiometry. These results, therefore, show that precise control of local stoichiometry is required to improve the stability of MAPbI3 and thus the lifetime of perovskite solar cells