The shortcomings of semi-local and hybrid functionals: what we can learn from surface science studies

A study of the adsorption of CO on late 4d and $5d$ transition metal (111) surfaces (Ru, Rh, Pd, Ag, Os, Ir, and Pt) considering atop and hollow site adsorption is presented. The applied functionals include the gradient corrected PBE and BLYP functional, and the corresponding hybrid Hartree-Fock density functionals HSE and B3LYP. We find that PBE based hybrid functionals (specifically HSE) yield, with the exception of Pt, the correct site order on all considered metals, but they also considerably overestimate the adsorption energies compared to experiment. On the other hand, the semi-local BLYP functional and the corresponding hybrid functional B3LYP yield very satisfactory adsorption energies and the correct adsorption site for all surfaces. We are thus faced with a Procrustean problem: the B3LYP and BLYP functionals seem to be the overall best choice for describing adsorption on metal surfaces, but they simultaneously fail to account well for the properties of the metal, vastly overestimating the equilibrium volume and underestimating the atomization energies. Setting out from these observations, general conclusions are drawn on the relative merits and drawbacks of various semi-local and hybrid functionals. The discussion includes a revised version of the PBE functional specifically optimized for bulk properties and surface energies (PBEsol), a revised version of the PBE functional specifically optimized to predict accurate adsorption energies (rPBE), as well as the aforementioned BLYP functional. We conclude that no semi-local functional is capable to describe all aspects properly, and including non-local exchange also only improves some, but worsens other properties.Comment: 12 pages, 6 figures; to be published in New Journal of Physic

Inquiry, Identity, and Integrity in a Biblical Studies Methods Course

In this study, a university professor, a high school teacher, and two teacher-candidates engage in an inquiry into the identity and integrity of the religious studies teacher. Using Charteris’s (2014) ‘epistemological shudders’ as a framework, the authors explore the experience of learning to teach Bible in Christian schools by paying attention to the ways in which their experience with the unfamiliar intersected with their taken-for-granted beliefs and perspectives. The authors believe such reflections on experience are essential in particular to teachers of the Bible in Christian schools, but also, more generally, for ongoing lifelong teacher growth. This paper offers insights into how inquiry can be used as a method in a teacher education context. It also serves as an example of the importance of the partnership between universities and schools in the education of future teachers

Why is a noble metal catalytically active? The role of the O-Ag interaction in the function of silver as an oxidation catalyst

Extensive density-functional theory calculations, and taking into account temperature and pressure, affords a comprehensive picture of the behavior and interaction of oxygen and Ag(111), and provides valuable insight into the function of silver as an oxidation catalyst. The obtained phase-diagram reveals the most stable species present in a given environment and thus identifies (and excludes) possibly active oxygen species. In particular, for the conditions of ethylene epoxidation, a thin oxide-like structure is most stable, suggesting that such atomic O species are actuating the catalysis, in contrast to hitherto proposed molecular-like species.Comment: 4 pages including 3 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Theory of heterogeneous catalytic reactivity using the cluster approximation

A review with 41 refs.; d. functional theory enables quant. computational anal. of reaction intermediates. The cluster approach makes application to heterogeneous catalysis possible. Examples from transition metal catalysis and zeolite catalysis will be discussed. In the case of transition metals cluster choices will be analyzed to simulate properties of the extended surface. The issue of coverage dependent reactivity and surface reconstruction will be discussed. The concept of adatom basicity in metal catalysis will be analyzed. It will be shown that the information obtained on the elementary reaction steps from cluster can be used to predict the overall rate of a catalytic reaction. In transition metal catalysis for an oscillatory reaction as the CO oxidn. reaction catalyzed by (100) it will be shown how knowledge on the elementary reaction rate consts. of surface reactions can be used to predict the overall rate of the reaction with help of the time dependent Monte Carlo method. In zeolite catalysis the anal. of the reaction mechanism of methanol conversion will be used to show the strength of the cluster approxn. for the case of a refractory oxide. The hydroisomerization reaction will be used to relate microscopic mol. information to the overall rate of a zeolite catalyzed reactio

Prioritising Local Governance: A Sociological Approach to Managing Organised Crime through Local Peace Mediation Processes

Drug-trafficking has historically funded armed rebellions in Mali and fuelled inter-ethnic and inter-clan conflict over control of drug-trafficking routes in Northern communities. The proceeds of drug-trafficking have also financed the local governance of northern communities in Mali in the absence of effective state governance. Because of community reliance on organised crime for local governance services, the efforts of the 2015 Bamako national peace process to stamp out organised crime using confrontational law enforcement strategies without providing alternative sources of local governance only fuelled Northern grievances against the state. Transformative approaches to peace mediation conducted at the local level – which use inclusive community-based dialogue and socio-economic development strategies to gradually turn criminal governance into legitimate governance – are required to effectively displace organised crime in Northern communities in the long-term. The security classifications currently relied upon by peace mediators to manage organised crime through national and local peace processes have limited capacity to inform transformative mediation because they remove organised crime from its socio-political context. This brief argues that sociological concepts and empirical analysis, which places organised crime in its social context and frames organised crime as a problem of local governance, can inform inclusive transformative local mediation focused on organised crime

Selective catalytic oxidation by heterogeneous transition metal catalysts

A review with 21 refs.; The reaction mechanisms of two transition metal catalyzed reactions are discussed: epoxidn. of ethylene prodn. and vinylacetate. In addn. short ref. will be made to methanol and CO oxidn. The surface reactions are related to the corresponding reactions in organometallic complexes. Also a relation between surface science model studies and surface reactivity will be made. Elementary surface reaction steps on surfaces will be highlighted; subsequently the main mechanistic issues in oxygen CH and OH bond activation will be describe

Quantum chemistry of surface chemical reactivity

The quantum chemist's and surface physicist's view of the surface chem. bond are illustrated by means of chemisorption of CO as an example with 23 refs. Between adsorbate and metal surface, bonding as well as antibonding orbital fragments are formed. For mols. the adsorption geometry is a sensitive function of the balance of the repulsive atop directing interaction, resulting from the occupation of antibonding orbital fragments, and the high coordination directing bonding interaction. The bonding contribution to the surface chem. bond energy relates to the surface group orbital local d. of states around the Fermi level, as long as the orbital interactions are weak. The concepts of Pauli repulsion and group orbital LDOS can be used to provide a quantum-chem. basis to metal promotio

THOU SHALL NOT BRUSH YOUR TEETH WHILE EATING BREAKFAST: A 7- STEP PROGRAM FOR RESEARCHERS PREVIOUSLY HURT IN DATA ANALYSIS

After years of providing statistical advice to fellow faculty members and graduate students, I have come to realize that it is not necessarily the big issues, but lack of knowledge of basic data analysis principles that get my clients into trouble. My claim is that if researchers and students internalized two basic definitions they would not have any problems analyzing most of their experiments. The definitions of Experimental Unit (EU) as the smallest physical unit to which a treatment may be applied and Experimental Error (Exp. Err.) as the variation among EUs treated alike are the basis for successful data analysis of experiments. I follow a seven-step data analysis program for my graduate student and faculty clients: (1) Understanding the experiment; (2) Checking the data; (3) Getting a feel for the data; (4) Checking underlying assumptions; (5) Testing; (6) Estimating; and (7) Interpreting results. Clients who have adhered to the program generally have had fewer problems than clients who, for some reason or another, did not get on board of the program. I will also touch on the implications for teaching experimental design and data analysis to non-statistics majors