Studies on heteroatom phosphorus–fluorine compounds

This thesis is concerned with phosphorus-fluorine compounds in which phosphorus has a coordination number of either four, five or six and with special emphasis on compounds substituted by heteroatom-containing organic groups. A new series of aryloxy-fluorophosphoranes of general formula RnPF2(OC6F5)3-n (where n = 0, 1, 2; R = Me, Ph, Me2N, Et2N) have been prepared from the reaction of the Lewis base silyl ether pentafluorophenyltrimethylsilyl ether with the Lewis acid fluorophosphoranes RnPF5-n (where n = 0, 1, 2; R = Me, Ph, Me2N, Et2N). In contrast to alkoxy-fluorophosphoranes, which are known to be thermally unstable, these new aryloxy-fluorophosphoranes are found to be stable. All the reactions discussed are characterised by multi-substitution contrasting to the substitution pattern for other heteroatom-fluorophosphoranes. An insight was obtained into the reaction of aryl trimethylsilyl ethers with fluorophosphoranes from the reaction of the fluorophosphoranes PhPF4 and Me2NPF4 with the silyl-ethers PhOSiMe3 and C6F5OSiMe3, respectively, in which it was ascertained that the reactions proceeded via trifluorophosphorane intermediates to give difluorophosphoranes as the only phosphorus–fluorine product. [Continues.

Competition between Kondo screening and indirect magnetic exchange in a quantum box

Nanoscale systems of metal atoms antiferromagnetically exchange coupled to several magnetic impurities are shown to exhibit an unconventional re-entrant competition between Kondo screening and indirect magnetic exchange interaction. Depending on the atomic positions of the magnetic moments, the total ground-state spin deviates from predictions of standard Ruderman-Kittel-Kasuya-Yosida perturbation theory. The effect shows up on an energy scale larger than the level width induced by the coupling to the environment and is experimentally verifiable by studying magnetic field dependencies.Comment: 5 pages, 2 figures, v3 with minor change

Unraveling Ethics: Reflections from a Community-based Participatory Research Project with Youth

There is limited literature describing the ethical dilemmas that arise when conducting community-based participatory research. The following provides a case example of ethical dilemmas that developed during a multi-method community-based participatory action research project with youth in Calgary, Alberta, Canada. Several ethical dilemmas emerged during the course of the study related to the community in which the research was being undertaken, the recruitment of participants, and the overall research process. As important are possible harm s that may arise when the researcher is no longer involved. These ethical dilemmas and potential solutions are discussed in relation to social work research and community-based practice to raise awareness about the essential role of community in informing ethical research practice

NEMLink: Augmenting the Australian National Electricity Market transmission grid to facilitate increased wind turbine generation and its effect on transmission congestion

Hewson, MG ORCiD: 0000-0002-5212-3921This report’s primary aim is to investigate ‘The effect of increasing the number of wind turbine generators on transmission line congestion in the Australian National Electricity Market from 2014 to 2025’. The report is part of the research project titled ‘An investigation of the impacts of increased power supply to the national grid by wind generators on the Australian electricity industry’. The sensitivity analysis in this report uses simulations from the ‘Australian National Electricity Market (ANEM) model version 1.10’ 10’ (Wild, Bell & Foster 2015) to model the effect of five different levels of wind penetration on transmission congestion. The five levels of wind penetration span Scenarios A to E where Scenario A represents ‘no wind’ and Scenario E includes all the existing and planned wind power sufficient to meet Australia’s 20% 2020 41TWh Large Renewable Energy Target. Wild, Bell and Foster (2015) provide a comprehensive explanation of the both the ANEM model and the five levels of wind penetration

Dynamical mean-field theory of indirect magnetic exchange

To analyze the physical properties arising from indirect magnetic exchange between several magnetic adatoms and between complex magnetic nanostructures on metallic surfaces, the real-space extension of dynamical mean-field theory (R-DMFT) appears attractive as it can be applied to systems of almost arbitrary geometry and complexity. While R-DMFT describes the Kondo effect of a single adatom exactly, indirect magnetic (RKKY) exchange is taken into account on an approximate level only. Here, we consider a simplified model system consisting of two magnetic Hubbard sites ("adatoms") hybridizing with a non-interacting tight-binding chain ("substrate surface"). This two-impurity Anderson model incorporates the competition between the Kondo effect and indirect exchange but is amenable to an exact numerical solution via the density-matrix renormalization group (DMRG). The particle-hole symmetric model at half-filling and zero temperature is used to benchmark R-DMFT results for the magnetic coupling between the two adatoms and for the magnetic properties induced in the substrate. In particular, the dependence of the local adatom and the nonlocal adatom-adatom static susceptibilities as well as the magnetic response of the substrate on the distance between the adatoms and on the strength of their coupling with the substrate is studied. We find both, excellent agreement with the DMRG data even on subtle details of the competition between RKKY exchange and the Kondo effect but also complete failure of the R-DMFT, depending on the parameter regime considered. R-DMFT calculations are performed using the Lanczos method as impurity solver. With the real-space extension of the two-site DMFT, we also benchmark a simplified R-DMFT variant.Comment: 14 pages, 8 figure

Inelastic effects in molecular junctions in the Coulomb and Kondo regimes: Nonequilibrium equation-of-motion approach

Inelastic effects in the Coulomb blockade and Kondo regimes of electron transport through molecular junctions are considered within a simple nonequilibrium equation-of-motion (EOM) approach. The scheme is self-consistent, and can qualitatively reproduce the main experimental observations of vibrational features in Coulomb blockade [H.Park et al., Nature 407, 57 (2000)] and Kondo [L.H.Yu et al., Phys. Rev. Lett. 93, 266802 (2004)] regimes. Considerations similar to the equilibrium EOM approach by Meir et al. [Phys. Rev. Lett. 66, 3048 (1991); ibid. 70, 2601 (1993)] are used on the Keldysh contour to account for the nonequilibrium nature of the junction, and dressing by appropriate Franck-Condon (FC) factors is used to account for vibrational features. Results of the equilibrium EOM scheme by Meir et al. are reproduced in the appropriate limit.Comment: 12 pages, 5 figure

Kondo effect in single-molecule magnet transistors

We present a careful and thorough microscopic derivation of the Kondo Hamiltonian for single-molecule magnets (SMMs) transistors. When the molecule is strongly coupled to metallic leads, we show that by applying a transverse magnetic field it is possible to topologically induce or quench the Kondo effect in the conductance of a SMM with either an integer or a half-integer spin S>1/2. This topological Kondo effect is due to the Berry phase interference between multiple quantum tunneling paths of the spin. We calculate the renormalized Berry phase oscillations of the two Kondo peaks as a function of the transverse magnetic field by means of the poor man's scaling. In particular, we show that the Kondo exchange interaction between itinerant electrons in the leads and the SMM pseudo spin 1/2 depends crucially on the SMM spin selection rules for the addition and subtraction of an electron and can range from antiferromagnetic to ferromagnetic. We illustrate our findings with the SMM Ni4, which we propose as a possible candidate for the experimental observation of the conductance oscillations

Transport through correlated quantum dots: An investigation using the functional renormalization group

Calculations using the (exact) fermionic functional renormalization group are usually truncated at the second order of the corresponding hierarchy of coupled ordinary differential equations. We present a method for the systematic determination of higher order vertex functions. This method is applied to a study of transport properties of various correlated quantum dot systems. It is shown that for large Coulomb correlations higher order vertex functions cannot be neglected, and a static approximation is insufficient.Comment: 10 figures, accepted by Phys. Rev.

Wind speed and electricity demand correlation analysis in the Australian National Electricity Market: Determining wind turbine generators’ ability to meet electricity demand without energy storage

This paper analyses wind speed and electricity demand correlation to determine the ability of wind turbine generators to meet electricity demand in the Australian National Electricity Market (NEM) without the aid of energy storage. With the proposed increases in the number of windfarms to meet the Large-scale Renewable Energy Target (LRET), this correlation study is formative to identifying price and power stability issues and determining what transmission structure is required to best facilitate the absorption of wind power. We calculate correlations between wind speed and electricity demand data for the years 2010 to 2012 using Weather Research & Forecasting Model (WRF 2015) wind speed data and Australian Energy Market Operator (AEMO) electricity demand data. We calculate state level correlations to identify potential bottlenecks in the interconnectors that link each state’s transmission network. The transmission lines within each state tend to be less of a constraint. We find a small temporal increase in correlation between electricity demand and wind speed. This we attribute to an unwitting renewable energy portfolio effect with the increase in solar PV and solar water heating. Strengthening this portfolio effect is the decline in manufacturing that makes household domestic demand relatively larger. Comparing our study with an earlier correlation analysis by Bannister and Wallace (2011) tends to confirm our initial findings. We find the most advantage from the lack of correlation between wind speed between the NEM’s peripheral states including Queensland, South Australia and Tasmania. Additionally, the correlation between electricity demand and wind speed is strongest between these states. Similarly, we find the most advantage from the lack of correlation between electricity demand in each of these states. The self-interest groups within Victoria and New South Wales and the transmission companies geographically contained within each state hinders the development of optimal interconnector capacity to maximise the benefit of wind power in the peripheral states and the NEM generally