Effect of hydrogen on ground state structures of small silicon clusters

We present results for ground state structures of small Si$_{n}$H (2 \leq \emph{n} \leq 10) clusters using the Car-Parrinello molecular dynamics. In particular, we focus on how the addition of a hydrogen atom affects the ground state geometry, total energy and the first excited electronic level gap of an Si$_{n}$ cluster. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen bonds with two silicon atoms only in Si$_{2}$H, Si$_{3}$H and Si$_{5}$H clusters, while in other clusters (i.e. Si$_{4}$H, Si$_{6}$H, Si$_{7}$H, Si$_{8}$H, Si$_{9}$H and Si$_{10}$H) hydrogen is bonded to only one silicon atom. Also in the case of a compact and closed silicon cluster hydrogen bonds to the cluster from outside. We find that the first excited electronic level gap of Si$_{n}$ and Si$_{n}$H fluctuates as a function of size and this may provide a first principles basis for the short-range potential fluctuations in hydrogenated amorphous silicon. Our results show that the addition of a single hydrogen can cause large changes in the electronic structure of a silicon cluster, though the geometry is not much affected. Our calculation of the lowest energy fragmentation products of Si$_{n}$H clusters shows that hydrogen is easily removed from Si$_{n}$H clusters.Comment: one latex file named script.tex including table and figure caption. Six postscript figure files. figure_1a.ps and figure_1b.ps are files representing Fig. 1 in the main tex

Managers’ Moral Struggle : A Case Study on Ethical Dilemmas and Ethical Decision-making in the Context of Immigration

This qualitative study explores the types of ethical dilemmas that Finnish managers working in reception centres for asylum seekers have encountered and whether the moral intensity of the ethical issues was observable in the ethical decision-making. It concludes that the majority of the managers interviewed encountered ethical dilemmas relating to the termination of reception services. The ethical dilemmas were stratified into seven groups: ambiguous or complete absence of relevant instructions, lack of support, conflicting values, withholding information, pressure, discretionary stress, and unjust decisions on asylum applications. In addition, various dimensions of moral intensity were observed in the managers’ ethical decision-making, indicating that they recognised the ethical aspects of their moral dilemmas. Finally, theoretical and practical implications, as well as limitations and future propositions, are discussed.peerReviewe