We have found that the energy bands of bulk copper can be fit equally well with a set of Hamiltonian parameters H, and overlap parameters S, , = 8;, . corresponding to Wannier basis functions or by a set (H,-, '. , S, ', . ) corresponding to atomic basis functions or by any of a continuum of sets (H', , ', S, ",) between (H,-", Sf~) and (H, , ', S;, '). Using the Wannier parameters in thin-film calculations we previously obtained surface-charge deficits of -0.198e, -0.269e, and -0.3S4e for the (111), (100), and (110) films, respectively. Using atomic parameters we obtain a surface-charge surplus of 0.256e for a (111)film. Using a set of intermediate parameters we obtain deviations from surface-charge neutrality of 0.0079e, -0.0013e, and -0.0452e for the (111),(100), and (110) films. We give a physical explanation of why one would expect a set of intermediate parameters to yield approximate surface-charge neutrality on all three surfaces. Exact surface-charge neutrality can be obtained by making small surface-parameter shifts. We discuss the effect of the new parameters on the surface states, the most interesting of which is the (111)state in the L2.-L, gap. It is shifted downward but still lies 0.1 eV above EF rather than the 0.4 eV below E"needed if it is to be used to explain the photoemission data of Gartland and Slagsvold.

We have performed a tight-binding calculation of the energy bands of a 41-layer ferromagnetic (100) iron thin film. The 23-matrix element parameters (for each spin) were obtained by fitting Tawil and Callaway's bulk band calculation at a large number of points. The diagonal matrix element parameters for the surface layers were then shifted by a constant amount to make the surface charge neutral. The energy bands were calculated at 256 points in the two-dimensional Brillouin zone (BZ) and the planar and total densities of states calculated. A detailed discussion of the surface states and resonances throughout the two-dimensional BZ is given.

Strategies adopted globally to mitigate the threat of COVID–19 have primarily involved lockdown measures with substantial economic and social costs with varying degrees of success. Morbidity patterns of COVID–19 variants have a strong association with age, while restrictive lockdown measures have association with negative mental health outcomes in some age groups. Reduced economic prospects may also afflict some age cohorts more than others. Motivated by this, we propose a model to describe COVID–19 community spread incorporating the role of age-specific social interactions. Through a flexible parameterisation of an age-structured deterministic Susceptible Exposed Infectious Removed (SEIR) model, we provide a means for characterising different forms of lockdown which may impact specific age groups differently. Social interactions are represented through age group to age group contact matrices, which can be trained using available data and are thus locally adapted. This framework is easy to interpret and suitable for describing counterfactual scenarios, which could assist policy makers with regard to minimising morbidity balanced with the costs of prospective suppression strategies. Our work originates from an Irish context and we use disease monitoring data from February 29th 2020 to January 31st 2021 gathered by Irish governmental agencies. We demonstrate how Irish lockdown scenarios can be constructed using the proposed model formulation and show results of retrospective fitting to incidence rates and forward planning with relevant “what if / instead of” lockdown counterfactuals. Uncertainty quantification for the predictive approaches is described. Our formulation is agnostic to a specific locale, in that lockdown strategies in other regions can be straightforwardly encoded using this model.

No abstract

We have performed a tight-binding calculation of the energy bands of a 29-layer (110) ferromagnetic iron thin film. The matrix parameters were obtained by fitting a bulk calculation of Tawil and Callaway with the diagonal surface matrix elements shifted by a constant amount to obtain surface charge neutrality. The energy bands were calculated at 117 points in the irreducible (one fourth) two-dimensional Brillouin zone. The planar and total densities of states are also reported and compared to previous results. A discussion of the surface states and energy bands is given and the structure of the energy bands is correlated to structure seen in the planar density of states and the effects of s-d hybridization.