Linear Metal Chains in Ca2M2X (M = Pd, Pt; X = Al, Ge): Origin of the Pairwise Distortion and Its Role in the Structure Stability

A series of four new analogue phases Ca2M2X (M = Pd, Pt and X = Al, Ge) were prepared by direct combination of the respective elements in stoichiometric mixtures at high temperature in order to analyze the impact of valence electron count (vec) and electronegativity differences (Δχ) on the structure selection and stability. Their crystal structures, as determined from single-crystal X-ray diffraction data, correspond to two different but closely related structure types. The first compound, Ca2Pd2Ge (I), is an unprecedented ternary ordered variant of the Zr2Al3-type (orthorhombic, Fdd2). The three other phases, Ca2Pt2Ge (II), Ca2Pd2Al (III) and Ca2Pt2Al (IV), adopt the Gd2Ge2Al-type structure (monoclinic, C2/c). All title structures feature linear chains of the noble metals (Pd or Pt). The Pd linear chains in I are undistorted with equidistant Pd···Pd atoms, whereas the metal chains in II–IV are pairwise distorted, resulting in short connected {Pd2} or {Pt2} dumbbells that are separated by longer M···M contacts. The occurrence and magnitude of the pairing distortion in these chains are controlled by the vec and the Δχ between the constituent elements, a result which is supported by analysis of the calculated Bader effective charges. The metal chains act as charge modulation units, critical for the stability and the electronic flexibility of the structures by an adequate adjustment of the metal–metal bond order to both the vec and the degree of charge transfer. Thus, Ca2Pd2Ge (28 ve/f.u) is a Zintl-like, charge optimized phase with formally zerovalent Pd atoms forming the undistorted metal chains; semimetallic properties are predicted by TB-LMTO calculations. In contrast, the isoelectronic Ca2Pt2Ge is predicted to be a good metal with the Fermi level located at a local maximum of the DOS, a fingerprint of potential electronic instability. This is due to greater charge transfer to the more electronegative Pt atoms forming the metal chains and probably to packing frustration in the well packed structure that may prevent a larger distortion of the Pt chains. However, the instability is suppressed in the aliovalent but isostructural phases Ca2M2Al (27 ve/f.u) with an enhancement of the pairing distortion within the metal chains but lower M–M bond order. Further reduction of the vec as in Ca2M2Cd (26 ve/f.u) may induce a transition toward the more geometrically flexible W2CoB2-type with a low dimensional structure, to create more room for a larger distortion of the metal chain as dictated by the shortage of valence electrons

On the Developer Adoption of Scrum: A New Acceptance Model for Agile Methodologies

In recent years, the agile Scrum methodology has become a popular software development approach. It significantly differs from traditional approaches as it promotes communication, self-organization, flexibility, and innovation instead of extensive planning and codified processes. While such a paradigm shift promises to better support the timely delivery of high-quality software in turbulent business environments, its success considerably depends on the willingness of developers to adopt the agile methodology. In this paper, we present a framework with drivers and inhibitors to the developer acceptance of Scrum. It combines analytical with empirical findings and can be used as a theoretical basis to empirically evaluate the actual support of Scrum in concrete scenarios. The introduced framework is based on the extended Technology Acceptance Model (TAM), which has been proven to be also applicable to describe the intention of developers to use a methodology. Building upon results from qualitative in-depth interviews with six experienced Scrum experts of a German DAX-30 company, we refine the general determinants of adoption contained in the TAM with several observed factors that influence the willingness of developers to use Scrum in practice

Reproducible computational biology experiments with SED-ML - The Simulation Experiment Description Markup Language

Background: The increasing use of computational simulation experiments to inform modern biological research creates new challenges to annotate, archive, share and reproduce such experiments. The recently published Minimum Information About a Simulation Experiment (MIASE) proposes a minimal set of information that should be provided to allow the reproduction of simulation experiments among users and software tools. Results: In this article, we present the Simulation Experiment Description Markup Language (SED-ML). SED-ML encodes in a computer-readable exchange format the information required by MIASE to enable reproduction of simulation experiments. It has been developed as a community project and it is defined in a detailed technical specification and additionally provides an XML schema. The version of SED-ML described in this publication is Level 1 Version 1. It covers the description of the most frequent type of simulation experiments in the area, namely time course simulations. SED-ML documents specify which models to use in an experiment, modifications to apply on the models before using them, which simulation procedures to run on each model, what analysis results to output, and how the results should be presented. These descriptions are independent of the underlying model implementation. SED-ML is a software-independent format for encoding the description of simulation experiments; it is not specific to particular simulation tools. Here, we demonstrate that with the growing software support for SED-ML we can effectively exchange executable simulation descriptions. Conclusions: With SED-ML, software can exchange simulation experiment descriptions, enabling the validation and reuse of simulation experiments in different tools. Authors of papers reporting simulation experiments can make their simulation protocols available for other scientists to reproduce the results. Because SED-ML is agnostic about exact modeling language(s) used, experiments covering models from different fields of research can be accurately described and combined