Correlation-Polarization Effects in Electron/Positron Scattering from Acetylene: A Comparison of Computational Models

Different computational methods are employed to evaluate elastic (rotationally summed) integral and differential cross sections for low energy (below about 10 eV) positron scattering off gas-phase C$_2$H$_2$ molecules. The computations are carried out at the static and static-plus-polarization levels for describing the interaction forces and the correlation-polarization contributions are found to be an essential component for the correct description of low-energy cross section behavior. The local model potentials derived from density functional theory (DFT) and from the distributed positron model (DPM) are found to produce very high-quality agreement with existing measurements. On the other hand, the less satisfactory agreement between the R-matrix (RM) results and measured data shows the effects of the slow convergence rate of configuration-interaction (CI) expansion methods with respect to the size of the CI-expansion. To contrast the positron scattering findings, results for electron-C$_2$H$_2$ integral and differential cross sections, calculated with both a DFT model potential and the R-matrix method, are compared and analysed around the shape resonance energy region and found to produce better internal agreement

Configuration-interaction calculations of positron binding to zinc and cadmium

The configuration-interaction method is applied to the study of positronic zinc (e+Zn) and positronic cadmium (e+Cd). The estimated binding energies and annihilation rates were 0.00373 hartree and 0.42×109 sec-1 for e+Zn and 0.006 10 hartree and 0.56×109 sec-1 for e+Cd. The low-energy elastic cross section and Zeff were estimated from a model potential that was tuned to the binding energies and annihilation rates. Since the scattering lengths were positive (14.5a0 for Zn and 11.6a0 for Cd) the differential cross sections are larger at backward angles than at forward angles just above threshold. The possibilities of measuring differential cross sections to confirm positron binding to these atoms is discussed

Grammar schools: a very English solution to a very English problem

The government’s decision to pass new legislation for the reintroduction of grammar schools took most people by surprise and was met with outcry by quite a few working in education. Details about how these new grammar schools would work in practice are still vague – in particular how they would avoid the traditional bias towards the middle classes. However what seems to stand out strongly in the debate is the generally negative response to this policy by the experts and even those in the Conservative Party. Despite this, Theresa May seems determined to push ahead with her plans, quite possibly because grammar schools are simply popular with the public. The cynic might well argue that the new prime minister wants to endear herself to the electorate – and what could be more convenient than to bring back a policy which resonates strongly with aspiring middle class and working class parents

Sociology of Education

‘An essential student-friendly text for Education Studies.’ Dr Gillian Forrester, Subject Head for Education & Early Childhood Studies, Liverpool John Moores University ‘Introducing students to the complexities of Education Studies is a difficult task and this book will go a long way to making it easier. I will definitely be recommending this to all my students.’ Kevin Brain, Programme Leader, Education Studies, Leeds Trinity University This textbook explains the basic principles of sociology and relates these concepts to today’s society and education system in order to deepen your understanding of how these issues affect our lives and the world we live in, encouraging you to think critically and to develop a ‘sociological imagination’. Coverage includes: the wider political and economic context for education in the UK, including an analysis of the reforms of the 2010 coalition government childhood, schooling and pupil voice non-traditional consideration of critical pedagogy, ‘race’ and gender the role of education in a multicultural society inequalities in educational opportunity in terms of class, ethnicity and disability. This is essential reading for students on undergraduate Education Studies degrees, and for sociology courses covering educational issues

A Crystalline Tri-thorium Cluster with σ-Aromatic Metal-Metal Bonding.

From PubMed via Jisc Publications RouterHistory: received 2020-12-07, accepted 2021-08-06Publication status: aheadofprintMetal-metal bonding is a widely studied area of chemistry , and has become a mature field spanning numerous d transition metal and main group complexes . In contrast, actinide-actinide bonding is predicted to be weak , being currently restricted to spectroscopically-detected gas-phase U and Th , U H and U H in frozen matrices at 6-7 Kelvin (K) , or fullerene-encapsulated U . Conversely, attempts to prepare thorium-thorium bonds in frozen matrices produced only ThH (n = 1-4) . Thus, there are no isolable actinide-actinide bonds under normal conditions. Computational investigations have explored the likely nature of actinide-actinide bonding , concentrating on localised σ-, π-, and δ-bonding models paralleling d transition metal analogues, but predictions in relativistic regimes are challenging and have remained experimentally unverified. Here, we report thorium-thorium bonding in a crystalline cluster, prepared and isolated under normal experimental conditions. The cluster exhibits a diamagnetic, closed-shell singlet ground-state with a valence-delocalised three-centre-two-electron σ-aromatic bond that is counter to the focus of previous theoretical predictions. The experimental discovery of actinide σ-aromatic bonding adds to main group and d transition metal analogues, extending delocalised σ-aromatic bonding to the heaviest elements in the periodic table and to principal quantum number six, and constitutes a new approach to elaborating actinide-actinide bonding. [Abstract copyright: © 2021. The Author(s), under exclusive licence to Springer Nature Limited.