Development of a Kohn-Sham like potential in the Self-Consistent Atomic Deformation Model

This is a brief description of how to derive the local ``atomic'' potentials from the Self-Consistent Atomic Deformation (SCAD) model density function. Particular attention is paid to the spherically averaged case.Comment: 5 Pages, LaTeX, no figure

Atomistic modelling of diffusion

This thesis describes the dimer method, which is an algorithm that can be used to find state transitions in an atomistic system, and the application of this method to two different atomistic diffusion problems. The dimer method is an algorithm that locates the saddle points of a potential field of arbitrary dimensionality. These saddle points correspond to the points of transition between metastable states of an atomistic system. A number of improvements to the algorithm of the dimer method have been described and implemented in this work. The first atomistic problem to be described is the diffusion of Au adatoms on a face-centred cubic Au(100) surface. By applying the dimer method to this system, a number of state transitions involving varying numbers of atoms are discovered, from the initial configuration of a single adatom on the surface and from configurations of two adatoms close together. [Continues.

Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with oxygen

Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with O-2. The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF6 bath gas, at five temperatures in the range 297-600 K. The second order rate constants at 10 Torr were fitted to the Arrhenius equation: log(k/cm(3) molecule(-1) s(-1)) = (-11.08 +/- 0.04) + (1.57 +/- 0.32 kJ mol(-1))/RT ln10 The decrease in rate constant values with increasing temperature, although systematic is very small. The rate constants showed slight increases in value with pressure at each temperature, but this was scarcely beyond experimental uncertainty. From estimates of Lennard-Jones collision rates, this reaction is occurring at ca. 1 in 20 collisions, almost independent of pressure and temperature. Ab initio calculations at the G3 level backed further by multi-configurational (MC) SCF calculations, augmented by second order perturbation theory (MRMP2), support a mechanism in which the initial adduct, H2SiOO, formed in the triplet state (T), undergoes intersystem crossing to the more stable singlet state (S) prior to further low energy isomerisation processes leading, via a sequence of steps, ultimately to dissociation products of which the lowest energy pair are H2O + SiO. The decomposition of the intermediate cyclo-siladioxirane, via O-O bond fission, plays an important role in the overall process. The bottleneck for the overall process appears to be the T -> S process in H2SiOO. This process has a small spin orbit coupling matrix element, consistent with an estimate of its rate constant of 1 x 10(9) s(-1) obtained with the aid of RRKM theory. This interpretation preserves the idea that, as in its reactions in general, SiH2 initially reacts at the encounter rate with O-2. The low values for the secondary reaction barriers on the potential energy surface account for the lack of an observed pressure dependence. Some comparisons are drawn with the reactions of CH2 + O-2 and SiCl2 + O-2

Diffusion dynamics of defects in Fe and Fe-P systems

The dimer method with the Ackland EAM potential has been used to determine the diffusion mechanisms of isolated defects in the bulk of α-Fe. Three defect systems were studied, an isolated vacancy, a P-vacancy complex and a P interstitial defect. Using an event table consisting of the transitions found using the dimer method, the kinetic Monte Carlo method has been used to simulate the diffusion of these defects. Periodic boundary conditions were used to simulate Fe crystals with finite concentrations of P atoms between 0.006 at. % and 0.038 at. %. At lower temperatures of around 350 K, substitutional P atoms in Fe act as centers of attraction for vacancy defects, such that the defect moves as a P-vacancy complex for most of the time. However, as the temperature is increased, the phosphorus atom and the vacancy spend greater amounts of time dissociated. We found that P interstitial defects can also diffuse through the lattice. Diffusion constants have been calculated for these systems at various temperatures and P concentrations. These showed that an Fe-P dumbbell is the most mobile of these defect systems and a P-vacancy complex the least mobile. For the isolated vacancy and P interstitial defect systems, the diffusion constant was found to satisfy the Arrhenius relation; the P-vacancy complex, however, showed a deviation from this relation

Lake and crannog : A 2500-year palaeoenvironmental record of continuity and change in NE Scotland

Acknowledgements Special acknowledgements go to Audrey Innes for her laboratory support, to Laura McHardie who originally extracted the core with Michael J. Stratigos. Thanks are owed to the Leys Estate and the then Estate Manager Thys Simpson for allowing access, help in taking the core and overall support for work in the former loch. Thanks to the Hunter Archaeological and Historical Trust who funded the fieldwork. The article was written as part of the Leverhulme Trust funded project ‘Comparative Kingship: the early Medieval kingdoms of Northern Britain and Ireland’ (Grant RG13876-10). Authors would like to thank the use of RIAIDT-USC analytical facilities. OLC is funded by JIN project (PID2019-111683RJ-I00) Spanish Ministerio de Ciencia e Innovacion and Beca Leonardo a Investigadores y Creadores Culturales 2020 de la Fundación BBVA. open access via Elsevier agreementPeer reviewedPublisher PD

III-V 4D Transistors

We fabricated for the first time vertically and laterally integrated III-V 4D transistors. III-V gate-all-around (GAA) nanowire MOSFETs with $3×4$ arrays show high drive current of $1.35mA/ \mu m$ and high transconductance of $0.85mS/ \mu m$. The vertical stacking of the III-V nanowires have provided an elegant solution to the drivability bottleneck of nanowire devices and is promising for future low-power logic and RF application.Chemistry and Chemical Biolog

Magnetic ordering of Mn sublattice, dense Kondo lattice behavior of Ce in (RPd3)8Mn (R = La, Ce)

We have synthesized two new interstitial compounds (RPd3)8Mn (R = La and Ce). The Mn ions present in "dilute" concentration of just 3 molar percent form a sublattice with an unusually large Mn-Mn near neighbor distance of ~ 85 nm. While the existence of (RPd3)8M (where M is a p-block element) is already documented in the literature, the present work reports for the first time the formation of this phase with M being a 3d element. In (LaPd3)8Mn, the Mn sub-lattice orders antiferromagnetically as inferred from the peaks in low-field magnetization at 48 K and 23 K. The latter peak progressively shifts towards lower temperatures in increasing magnetic field and disappears below 1.8 K in a field of ~ 8 kOe. On the other hand in (CePd3)8Mn the Mn sublattice undergoes a ferromagnetic transition around 35 K. The Ce ions form a dense Kondo-lattice and are in a paramagnetic state at least down to 1.5 K. A strongly correlated electronic ground state arising from Kondo effect is inferred from the large extrapolated value of C/T = 275 mJ/Ce-mol K^2 at T = 0 K. In contrast, the interstitial alloys RPd3Mnx (x = 0.03 and 0.06), also synthesized for the first time, have a spin glass ground state due to the random distribution of the Mn ions over the available "1b" sites in the parent RPd3 crystal lattice.Comment: 18 figures and 20 pages of text documen

Deaf, Dumb, and Chatting Robots, Enabling Distributed Computation and Fault-Tolerance Among Stigmergic Robot

We investigate ways for the exchange of information (explicit communication) among deaf and dumb mobile robots scattered in the plane. We introduce the use of movement-signals (analogously to flight signals and bees waggle) as a mean to transfer messages, enabling the use of distributed algorithms among the robots. We propose one-to-one deterministic movement protocols that implement explicit communication. We first present protocols for synchronous robots. We begin with a very simple coding protocol for two robots. Based on on this protocol, we provide one-to-one communication for any system of n \geq 2 robots equipped with observable IDs that agree on a common direction (sense of direction). We then propose two solutions enabling one-to-one communication among anonymous robots. Since the robots are devoid of observable IDs, both protocols build recognition mechanisms using the (weak) capabilities offered to the robots. The first protocol assumes that the robots agree on a common direction and a common handedness (chirality), while the second protocol assumes chirality only. Next, we show how the movements of robots can provide implicit acknowledgments in asynchronous systems. We use this result to design asynchronous one-to-one communication with two robots only. Finally, we combine this solution with the schemes developed in synchronous settings to fit the general case of asynchronous one-to-one communication among any number of robots. Our protocols enable the use of distributing algorithms based on message exchanges among swarms of Stigmergic robots. Furthermore, they provides robots equipped with means of communication to overcome faults of their communication device

Optimally squeezed spin states

We consider optimally spin-squeezed states that maximize the sensitivity of the Ramsey spectroscopy, and for which the signal to noise ratio scales as the number of particles $N$. Using the variational principle we prove that these states are eigensolutions of the Hamiltonian $H(\lambda)=\lambda S_z^2-S_x,$ and that, for large $N$, the states become equivalent to the quadrature squeezed states of the harmonic oscillator. We present numerical results that illustrate the validity of the equivalence

Discrimination, labour markets and the Labour Market Prospects of Older Workers: What Can a Legal Case Teach us?

As governments become increasingly concerned about the fiscal implications of the ageing population, labour market policies have sought to encourage mature workers to remain in the labour force. The ‘human capital’ discourses motivating these policies rest on the assumption that older workers armed with motivation and vocational skills will be able to return to fulfilling work. This paper uses the post-redundancy recruitment experiences of former Ansett Airlines flight attendants to develop a critique of these expectations. It suggests that policies to increase older workers’ labour market participation will not succeed while persistent socially constructed age- and gender- typing shape labour demand. The conclusion argues for policies sensitive to the institutional structures that shape employer preferences, the competitive rationality of discriminatory practices, and the irresolvable tension between workers’ human rights and employers’ property rights