Accuracy control in ultra-large-scale electronic structure calculation

Numerical aspects are investigated in ultra-large-scale electronic structure calculation. Accuracy control methods in process (molecular-dynamics) calculation are focused. Flexible control methods are proposed so as to control variational freedoms, automatically at each time step, within the framework of generalized Wannier state theory. The method is demonstrated in silicon cleavage simulation with 10^2-10^5 atoms. The idea is of general importance among process calculations and is also used in Krylov subspace theory, another large-scale-calculation theory.Comment: 8 pages, 3 figures. To appear in J.Phys. Condens. Matter. A preprint PDF file in better graphics is available at http://fujimac.t.u-tokyo.ac.jp/lses/index_e.htm

Adding Gauge Fields to Kaplan's Fermions

We experiment with adding dynamical gauge field to Kaplan (defect) fermions. In the case of U(1) gauge theory we use an inhomogenous Higgs mechanism to restrict the 3d gauge dynamics to a planar 2d defect. In our simulations the 3d theory produce the correct 2d gauge dynamics. We measure fermion propagators with dynamical gauge fields. They posses the correct chiral structure. The fermions at the boundary of the support of the gauge field (waveguide) are non-chiral, and have a mass two times heavier than the chiral modes. Moreover, these modes cannot be excited by a source at the defect; implying that they are dynamically decoupled. We have also checked that the anomaly relation is fullfilled for the case of a smooth external gauge field. This is an uuencoded ps-file. Use 'uudecode hepchiral.ps.Z' and 'uncompress hepchiral.ps.Z' to produce the psfile.Comment: AZPH-TH/93-34, Lattice'93 poster,4 pages postscrip

Developing a pedagogical model for health-based Physical Education

Despite global support for the role of physical education in health promotion, if we judge the subject against this goal alone, the profession has failed. Whilst multiple goals of the subject are acknowledged, this study positioned valuing a physically active life as the priority. However, physical education is characterised by multi-activity, technique-focused, sport-based curricula. Furthermore, when teachers modify their practice with specific health goals in mind, this often takes a fitness for sport and performance focus, despite a vision of promoting healthy, active lifestyles. This study builds on the groundwork of Haerens et al. (2011) who advocated for and initiated the first steps towards the development of a pedagogical model for Health-Based Physical Education. It aimed to develop a comprehensive evidence-informed pedagogical model, and to support teachers in the design, implementation and evaluation of the first school-based programmes using this model. Taking an eight-stage process to the pedagogical model development, this research drew on practitioner research, and most specifically, participatory action research, as its predominant methodology. Multiple and predominantly qualitative methods drew on Brookfield s (1995) four lenses: self-reflection, the experiences of teachers and students and the theoretical literature. Study participants were nine specialist physical education teachers and 263 students (161 male, 102 female, aged 11-14 years) from two diverse schools in the east of England. The findings present the types of programmes designed and implemented after teachers introduction to a theoretically-informed conceptual framework for Health-Based Physical Education. The impact of the programmes on students is considered against the four main goals of the model the development of habitual, motivated, informed and critical movers. The pedagogical model provides a comprehensive evidence-informed framework to support teachers to effectively promote positive physical activity behaviours in young people. It aims to support young people to be habitual, motivated, informed and critical movers. This model offers a new opportunity for physical education as there is currently no pedagogical model which forefronts valuing a physically active life as its primary goal

Analytical solution for capacitance calculation of a curved patch capacitor that conforms to the curvature of a homogeneous cylindrical dielectric rod

This Letter presents an analytical expression for the capacitance of a curved patch capacitor whose electrodes conform to the curvature of a long, homogeneous, cylindrical dielectric rod. The capacitor is composed of two infinitely long curved electrodes, symmetrically placed about a diameter of the cylinder cross-section. The resulting capacitance per unit length depends on both the dielectric properties of the material under test and the capacitor configuration. A practical capacitance measurement is also presented, with appropriately guarded finite electrodes. Very good agreement between measured and theoretically predicted capacitances were observed, to within 2.4 percent. The analytical result presented in this Letter can be applied for extremely rapid evaluation of rod permittivity from measured capacitance

Linear-scaling first-principles molecular dynamics of complex biological systems with the CONQUEST code

The recent progress of linear-scaling or $\mathcal{O}(N)$ methods in density functional theory (DFT) is remarkable. In this paper, we show that all-atom molecular dynamics simulations of complex biological systems based on DFT are now possible using our linear-scaling DFT code Conquest. We first overview the calculation methods used in Conquest and explain the method introduced recently to realise efficient and robust first-principles molecular dynamics (FPMD) with $\mathcal{O}(N)$ DFT. Then, we show that we can perform reliable all-atom FPMD simulations of a hydrated DNA model containing about 3400 atoms. We also report that the velocity scaling method is both reliable and useful for controlling the temperature of the FPMD simulation of this system. From these results, we conclude that reliable FPMD simulations of complex biological systems are now possible with Conquest

The pseudoatomic orbital basis: electronic accuracy and soft-mode distortions in ABO3 perovskites

The perovskite oxides are known to be susceptible to structural distortions over a long wavelength when compared to their parent cubic structures. From an ab initio simulation perspective, this requires accurate calculations including many thousands of atoms; a task well beyond the remit of traditional plane wave-based density functional theory (DFT). We suggest that this void can be filled using the methodology implemented in the large-scale DFT code, CONQUEST, using a local pseudoatomic orbital (PAO) basis. Whilst this basis has been tested before for some structural and energetic properties, none have treated the most fundamental quantity to the theory, the charge density n(r) itself. An accurate description of n(r) is vital to the perovskite oxides due to the crucial role played by short-range restoring forces (characterised by bond covalency) and long range Coulomb forces as suggested by the soft-mode theory of Cochran and Anderson. We find that modestly sized basis sets of PAOs can reproduce the plane-wave charge density to a total integrated error of better than 0.5% and provide Bader partitioned ionic charges, volumes and average charge densities to similar degree of accuracy. Further, the multi-mode antiferroelectric distortion of PbZrO3 and its associated energetics are reproduced by better than 99% when compared to plane-waves. This work suggests that electronic structure calculations using efficient and compact basis sets of pseudoatomic orbitals can achieve the same accuracy as high cutoff energy plane-wave calculations. When paired with the CONQUEST code, calculations with high electronic and structural accuracy can now be performed on many thousands of atoms, even on systems as delicate as the perovskite oxides

Large-scale electronic structure theory for simulating nanostructure process

Fundamental theories and practical methods for large-scale electronic structure calculations are given, in which the computational cost is proportional to the system size. Accuracy controlling methods for microscopic freedoms are focused on two practical solver methods, Krylov-subspace method and generalized-Wannier-state method. A general theory called the 'multi-solver' scheme is also formulated, as a hybrid between different solver methods. Practical examples are carried out in several insulating and metallic systems with 10^3-10^5 atoms. All the theories provide general guiding principles of constructing an optimal calculation for simulating nanostructure processes, since a nanostructured system consists of several competitive regions, such as bulk and surface regions, and the simulation is designed to reproduce the competition with an optimal computational cost.Comment: 19 pages, 6 figures. To appear in J. Phys. Cond. Matt. A preprint PDF file in better graphics is available at http://fujimac.t.u-tokyo.ac.jp/lses/index_e.htm