610 research outputs found
Understanding Homeowners' Renovation Decisions::Findings of the VERD Project
The VERD Study: In October 2011, the VERD project team at the University of East Anglia began a two-year research project investigating homeowners’ renovation decisions, funded by the UK Energy Research Centre (UKERC). This report and public conference summarises the findings, revealing why homeowners renovate and why they decide to improve their home energy efficiency
Electronic structure and total energy of interstitial hydrogen in iron: Tight binding models
An application of the tight binding approximation is presented for the
description of electronic structure and interatomic force in magnetic iron,
both pure and containing hydrogen impurities. We assess the simple canonical
d-band description in comparison to a non orthogonal model including s and d
bands. The transferability of our models is tested against known properties
including the segregation energies of hydrogen to vacancies and to surfaces of
iron. In many cases agreement is remarkably good, opening up the way to quantum
mechanical atomistic simulation of the effects of hydrogen on mechanical
properties
Reconstruction of 2D Al Ti on TiB in an aluminium melt
It has been widely considered that Al Ti is involved in the aluminium nucleation on TiB , although the mechanism has not been fully understood. In this paper molecular dynamics has been conducted to investigate this phenomenon at an atomistic scale. It was found that a two-dimensional Al Ti layer may remain on TiB above the aluminium liquidus. In addition, the results showed that this 2D Al Ti undergoes interface reconstruction by forming a triangular pattern. This triangular pattern consists of different alternative stacking sequences. The transition region between the triangles forms an area of strain concentration. By means of this mechanism, this interfacial Al Ti layer stabilizes itself by localizing the large misfit strain between TiB and Al Ti This reconstruction is similar to the hdp-fcc interface reconstruction in other systems which has been observed experimentally.EPSR
Single-Particle Dynamics in the Vicinity of the Mott-Hubbard Metal-to-Insulator Transition
The single-particle dynamics close to a metal-to-insulator transition induced
by strong repulsive interaction between the electrons is investigated. The
system is described by a half-filled Hubbard model which is treated by dynamic
mean-field theory evaluated by high-resolution dynamic density-matrix
renormalization. We provide theoretical spectra with momentum resolution which
facilitate the comparison to photoelectron spectroscopy.Comment: 22 pages, 24 figures, comprehensive high-resolution study of single
electron dynamics around a Mott metal-insulator transition, with momentum
resolved spectral densities; slight changes due to referees' suggestion
Magnetism: the Driving Force of Order in CoPt. A First-Principles Study
CoPt or FePt equiatomic alloys order according to the tetragonal L10
structure which favors their strong magnetic anisotropy. Conversely magnetism
can influence chemical ordering. We present here {\it ab initio} calculations
of the stability of the L10 and L12 structures of Co-Pt alloys in their
paramagnetic and ferromagnetic states. They show that magnetism strongly
reinforces the ordering tendencies in this system. A simple tight-binding
analysis allows us to account for this behavior in terms of some pertinent
parameters
Stacking Characteristics of Close Packed Materials
It is shown that the enthalpy of any close packed structure for a given
element can be characterised as a linear expansion in a set of continuous
variables which describe the stacking configuration. This enables us
to represent the infinite, discrete set of stacking sequences within a finite,
continuous space of the expansion parameters . These determine the
stable structure and vary continuously in the thermodynamic space of pressure,
temperature or composition. The continuity of both spaces means that only
transformations between stable structures adjacent in the space are
possible, giving the model predictive and well as descriptive ability. We
calculate the using density functional theory and interatomic potentials
for a range of materials. Some striking results are found: e.g. the
Lennard-Jones potential model has 11 possible stable structures and over 50
phase transitions as a function of cutoff range. The very different phase
diagrams of Sc, Tl, Y and the lanthanides are understood within a single
theory. We find that the widely-reported 9R-fcc transition is not allowed in
equilibrium thermodynamics, and in cases where it has been reported in
experiments (Li, Na), we show that DFT theory is also unable to predict it
Иноязычная коммуникативная компетенция современного преподавателя технического вуза
В статье рассматриваются организационно-педагогические и методические условия формирования иноязычной коммуникативной компетенции преподавателя технического вуза на примере реализации программы повышения квалификации "Формирование профессиональной дидактической компетенции средствами английского языка". Иностранный язык становится инструментом для выполнения профессиональной деятельности современного преподавателя технического вуза
Error estimates for solid-state density-functional theory predictions: an overview by means of the ground-state elemental crystals
Predictions of observable properties by density-functional theory
calculations (DFT) are used increasingly often in experimental condensed-matter
physics and materials engineering as data. These predictions are used to
analyze recent measurements, or to plan future experiments. Increasingly more
experimental scientists in these fields therefore face the natural question:
what is the expected error for such an ab initio prediction? Information and
experience about this question is scattered over two decades of literature. The
present review aims to summarize and quantify this implicit knowledge. This
leads to a practical protocol that allows any scientist - experimental or
theoretical - to determine justifiable error estimates for many basic property
predictions, without having to perform additional DFT calculations. A central
role is played by a large and diverse test set of crystalline solids,
containing all ground-state elemental crystals (except most lanthanides). For
several properties of each crystal, the difference between DFT results and
experimental values is assessed. We discuss trends in these deviations and
review explanations suggested in the literature. A prerequisite for such an
error analysis is that different implementations of the same first-principles
formalism provide the same predictions. Therefore, the reproducibility of
predictions across several mainstream methods and codes is discussed too. A
quality factor Delta expresses the spread in predictions from two distinct DFT
implementations by a single number. To compare the PAW method to the highly
accurate APW+lo approach, a code assessment of VASP and GPAW with respect to
WIEN2k yields Delta values of 1.9 and 3.3 meV/atom, respectively. These
differences are an order of magnitude smaller than the typical difference with
experiment, and therefore predictions by APW+lo and PAW are for practical
purposes identical.Comment: 27 pages, 20 figures, supplementary material available (v5 contains
updated supplementary material
Half-metallic ferromagnetism and structural stability of zincblende phases of the transition-metal chalcogenides
An accurate density-functional method is used to study systematically
half-metallic ferromagnetism and stability of zincblende phases of
3d-transition-metal chalcogenides. The zincblende CrTe, CrSe, and VTe phases
are found to be excellent half-metallic ferromagnets with large half-metallic
gaps (up to 0.88 eV). They are mechanically stable and approximately 0.31-0.53
eV per formula unit higher in total energy than the corresponding
nickel-arsenide ground-state phases, and therefore would be grown epitaxially
in the form of films and layers thick enough for spintronic applications.Comment: 4 pages with 4 figures include
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