Multicomponent multisublattice alloys, nonconfigurational entropy and other additions to the Alloy Theoretic Automated Toolkit

A number of new functionalities have been added to the Alloy Theoretic Automated Toolkit (ATAT) since it was last reviewed in this journal in 2002. ATAT can now handle multicomponent multisublattice alloy systems, nonconfigurational sources of entropy (e.g. vibrational and electronic entropy), Special Quasirandom Structures (SQS) generation, tensorial cluster expansion construction and includes interfaces for multiple atomistic or ab initio codes. This paper presents an overview of these features geared towards the practical use of the code. The extensions to the cluster expansion formalism needed to cover multicomponent multisublattice alloys are also formally demonstrated.Comment: Code available from http://www.alum.mit.edu/www/avdw/ata

De toegankelijkheidsdiscussie voorbij?

Elke sector heeft wel zo’n discussiethema dat blijft opduiken. Bij ons is dat ‘de (on) toegankelijkheid van het jeugdwerk’. Ondanks de vele inkt die hierover reeds is gevloeid, blijft men onzeker over wat men met die ontoegankelijkheid aan moet. In 2007 startte ik een doctoraatsstudie aan de vakgroep Sociale Agogiek, die uiteindelijk als titel kreeg: ‘Jeugdwerk en sociale uitsluiting. De toegankelijkheidsdiscussie voorbij?’. Voor Krax de bevindingen in vogelvlucht

Editorialising practices, competitive marketablility and James Thomson's 'The seasons'

The lapse of Andrew Millar's copyright for James Thomson's The Seasons in 1765 resulted in an increasing number of new editions of the poem being published in the late eighteenth century. This article compares the print-cultural make-ups of three editions of The Seasons that were issued in the 1790s. An examination of the print-cultural differences between these publishing ventures reveals distinct editorial practices and marketing strategies. In an attempt to increase the attractiveness of their editions with visual and textual paraphernalia, the producers developed their own versions' of The Seasons and, in the process, fashioned new interpretations of Thomson's poem

Testing Vietnam's public safety net

An effective public safety net can be important in a poor transition economy such as Vietnam. Yet we know very little about the performance of existing public transfers as a safety net. Using panel data, the paper investigates whether Vietnam's main social welfare transfers promoted poor people out of poverty and whether they protected the non-poor from becoming poor. It also explores the role transfer programs played in the country's dramatic reduction of poverty in the 1990s. Counterfactual consumption levels without transfers allow for behavioral responses. The findings suggest that transfer programs helped few people escape poverty and protected even fewer from falling into poverty. The public safety net appears to have been largely irrelevant to the country's recent poverty reduction record.Services&Transfers to Poor,Rural Poverty Reduction,Safety Nets and Transfers,Poverty Assessment,Environmental Economics&Policies

Protecting the poor in Vietnam's emerging market economy

Poverty Assessment,Environmental Economics&Policies,Rural Poverty Reduction,Safety Nets and Transfers,Services&Transfers to Poor

Assessing the welfare impacts of public spending

An important objective of public spending is to raise household living standards, particularly for the poor. But how can final impacts on this objective best be assessed? Evaluating a policy's impact requires assessing how different things would have been in its absence. But the counterfactual of no intervention is tricky to quantify. The author surveys the methods most often used to assess the welfare effects of public spending. Limitations of current practices are studied and implications for future best practices are drawn. The methods used to assess welfare impacts broadly fall into two groups: benefit incidence studies and behavioral approaches. Benefit incidence studies ignore behavioral responses and second-round effects, using the provision cost as a proxy for benefits received. Behavioral approaches present quite different drawbacks, in attempting to represent individual benefits correctly. A number of recent studies usefully combine both approaches. It is still uncertain whether behaviorally consistent methods actually point to fundamentally different policy recommendations. What can be concluded is that we need to diversify and compare results from our evaluation methods and broaden our definition of well-being, to see how various facets of living standard are affected by public spending.Public Health Promotion,Environmental Economics&Policies,Health Economics&Finance,Economic Theory&Research,Decentralization,Poverty and Social Impact Analysis,Health Economics&Finance,Poverty Monitoring&Analysis,Environmental Economics&Policies,Economic Theory&Research

Breastfeeding and popular aetiology in the Sahel

Two views about breastfeeding and the resumption of intercourse after a birth are found to prevail in Bamako and Bobo-Dioulasso, two cities of the Sahel region of Africa: that sexual relations may spoil the milk; and that a child should be weaned when the woman is pregnant again. Both beliefs provide a rationale to abstain, but the postpartum taboo has been greatly reduced in the area, and the second belief is the most important. ‘Bad milk’ serves as an explanation for many of the diarrhoeas and diseases of nutritional origin that affect infants and children. Traditional medical treatments of diarrhoea and protein calorie malnutrition are consistent with the popular aetiology. The acceptance of modern techniques of infant care in this area may well be predicated on the diffusion of an alternative model of disease causation

Automating first-principles phase diagram calculations

Devising a computational tool that assesses the thermodynamic stability of materials is among the most important steps required to build a “virtual laboratory,” where materials could be designed from first principles without relying on experimental input. Although the formalism that allows the calculation of solid-state phase diagrams from first principles is well established, its practical implementation remains a tedious process. The development of a fully automated algorithm to perform such calculations serves two purposes. First, it will make this powerful tool available to a large number of researchers. Second, it frees the calculation process from arbitrary parameters, guaranteeing that the results obtained are truly derived from the underlying first-principles calculations. The proposed algorithm formalizes the most difficult step of phase diagram calculations, namely the determination of the “cluster expanison,” which is a compact representation of the configurational dependence of the alloy’s energy. This is traditionally achieved by a fit of the unknown interaction parameters of the cluster expansion to a set of structural energies calculated from first principles. We present a formal statistical basis for the selection of both the interaction parameters to include in the cluster expansion and the structures to use to determine them. The proposed method relies on the concepts of cross-validation and variance minimization. An application to the calculation of the phase diagram of the Si-Ge, CaO-MgO, Ti-Al, and Cu-Au systems is presented

Realistic time-scale fully atomistic simulations of surface nucleation of dislocations in pristine nanopillars

We use our recently proposed accelerated dynamics algorithm (Tiwary and van de Walle, 2011) to calculate temperature and stress dependence of activation free energy for surface nucleation of dislocations in pristine Gold nanopillars under realistic loads. While maintaining fully atomistic resolution, we achieve the fraction of a second time-scale regime. We find that the activation free energy depends significantly and non-linearly on the driving force (stress or strain) and temperature, leading to very high activation entropies. We also perform compression tests on Gold nanopillars for strain-rates varying between 7 orders of magnitudes, reaching as low as 10^3/s. Our calculations bring out the perils of high strain-rate Molecular Dynamics calculations: we find that while the failure mechanism for compression of Gold nanopillars remains the same across the entire strain-rate range, the elastic limit (defined as stress for nucleation of the first dislocation) depends significantly on the strain-rate. We also propose a new methodology that overcomes some of the limits in our original accelerated dynamics scheme (and accelerated dynamics methods in general). We lay out our methods in sufficient details so as to be used for understanding and predicting deformation mechanism under realistic driving forces for various problems