Simple implementation of complex functionals: scaled selfconsistency

We explore and compare three approximate schemes allowing simple implementation of complex density functionals by making use of selfconsistent implementation of simpler functionals: (i) post-LDA evaluation of complex functionals at the LDA densities (or those of other simple functionals); (ii) application of a global scaling factor to the potential of the simple functional; and (iii) application of a local scaling factor to that potential. Option (i) is a common choice in density-functional calculations. Option (ii) was recently proposed by Cafiero and Gonzalez. We here put their proposal on a more rigorous basis, by deriving it, and explaining why it works, directly from the theorems of density-functional theory. Option (iii) is proposed here for the first time. We provide detailed comparisons of the three approaches among each other and with fully selfconsistent implementations for Hartree, local-density, generalized-gradient, self-interaction corrected, and meta-generalized-gradient approximations, for atoms, ions, quantum wells and model Hamiltonians. Scaled approaches turn out to be, on average, better than post-approaches, and unlike these also provide corrections to eigenvalues and orbitals. Scaled selfconsistency thus opens the possibility of efficient and reliable implementation of density functionals of hitherto unprecedented complexity.Comment: 12 pages, 1 figur

Systematic investigation of a family of gradient-dependent functionals for solids

Eleven density functionals are compared with regard to their performance for the lattice constants of solids. We consider standard functionals, such as the local-density approximation and the Perdew-Burke-Ernzerhof (PBE) generalized-gradient approximation (GGA), as well as variations of PBE GGA, such as PBEsol and similar functionals, PBE-type functionals employing a tighter Lieb-Oxford bound, and combinations thereof. Several of these variations are proposed here for the first time. On a test set of 60 solids we perform a system-by-system analysis for selected functionals and a full statistical analysis for all of them. The impact of restoring the gradient expansion and of tightening the Lieb-Oxford bound is discussed, and confronted with previous results obtained from other codes, functionals or test sets. No functional is uniformly good for all investigated systems, but surprisingly, and pleasingly, the simplest possible modifications to PBE turn out to have the most beneficial effect on its performance. The atomization energy of molecules was also considered and on a testing set of six molecules, we found that the PBE functional is clearly the best, the others leading to strong overbinding

Qualidade tecnológica da pluma do algodoeiro herbáceo cultivado com biossólidos.

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Precision measurement of the half-life and the decay branches of 62Ga

In an experiment performed at the Accelerator Laboratory of the University of Jyvaskyla, the beta-decay half-life of 62Ga has been studied with high precision using the IGISOL technique. A half-life of T1/2 = 116.09(17)ms was measured. Using beta-gamma coincidences, the gamma intensity of the 954keV transition and an upper limit of the beta-decay feeding of the 0+_2 state have been extracted. The present experimental results are compared to previous measurements and their impact on our understanding of the weak interaction is discussed.Comment: 7 pages, 7 figures, submitted to EPJ

Simultaneous selection of cupuassu tree and Brazilian mahogany genotypes in an agroforestry system in Pará state, Brazil.

Este trabalho teve por objetivo avaliar e selecionar progênies e matrizes de irmãos completos de cupuaçuzeiro e, simultaneamente, selecionar matrizes de mogno brasileiro com características superiores, para utilização em sistemas agroflorestais (SAFs). Foram avaliadas 25 progênies de irmãos completos de cupuaçuzeiro e uma progênie de meio irmão de mogno brasileiro. O estudo foi conduzido por 14 anos em uma propriedade comercial em Tomé Açu, Pará. Para o cupuaçuzeiro, foram utilizadas como variáveis de resposta o número e a produção de frutos por planta, e a taxa de plantas com sintomas da doença vassoura-de-bruxa. Para o mogno, empregou-se a altura total, altura comercial, altura da copa, DAP e volume de madeira comercial. Os resultados revelaram cinco progênies de cupuaçuzeiro com características interessantes para emprego em SAFs. Com base nos altos valores observados na acurácia de seleção e herdabilidade, inferimos um bom potencial de seleção de indivíduos promissores na população de cupuaçuzeiro. Dez matrizes de cupuaçuzeiro foram selecionadas com base no ranqueamento dos valores genotípicos e desempenho agronômico. Para o mogno brasileiro, três matrizes apresentaram ótimo desempenho silvicultural. As matrizes destas duas espécies deverão ser propagadas vegetativamente, para avaliação em ensaios clonais

Integrated geoinformation model for environmental planning in Rio de Janeiro, RJ, Brazil.

The design of an integrated geoinformation model was established to the environmental planning context, which is conduced by the Rio de Janeiro Municipal Secretariat for the Environment. Modelling boundaries were set from a semi-detailed soil survey executed by Embrapa Solos. This particular study aimed to evaluate the consistence of the GIS application as integrated part of the planning process. Therefore, the main objective was to identify weakness of existing procedures where the original data set could be revised by the proposed model. In addition, it was meant to explore object-oriented methodology applied to evaluate results from integrated spatial analysis according to existing products from survey methods. The methodological approach applies terrain object modelling standards in Molenaar (1996) and UML language for analysis and design (Rational, 1997). Yet, an integrated GIS environment supported by object-oriented technology (ILWIS 2.1 ®) was used to implement the conceptual model processes. Results are an updated semi-detailed soil map, at 1:75,000 scale, and derived information as land suitability for horticulture and reforestation, land vulnerability, and land environmental quality. Further spatial analysis were defined to support reclassification, aggregation, generalisation, and overlay processes for land suitability and land vulnerability interpretations. DTM analysis helped to review where the county area is classified either as highlands, due to erosion susceptibility, or as low lands, due to drainage conditions. Image analysis has considered supervised classification to extract update land cover information that helps to evaluate environmental quality of the lands

Crescimento inicial de genótipos de mamoneira com sementes submetidas ao envelhecimento acelerado.

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Separation of the Exchange-Correlation Potential into Exchange plus Correlation: an Optimized Effective Potential Approach

Most approximate exchange-correlation functionals used within density functional theory are constructed as the sum of two distinct contributions for exchange and correlation. Separating the exchange component from the entire functional is useful since, for exchange, exact relations exist under uniform density scaling and spin scaling. In the past, accurate exchange-correlation potentials have been generated from essentially exact densities constructed using information from either quantum chemistry or quantum Monte Carlo calculations but they have not been correctly decomposed into their separate exchange and correlation components, except for two-electron systems. exchange and correlation components (except for two-electron systems). Using a recently proposed method, equivalent to the solution of an optimized effective potential problem with the corresponding orbitals replaced by the exact Kohn-Sham orbitals, we obtain the separation according to the density functional theory definition. We compare the results for the Ne and Be atoms with those obtained by the previously used approximate separation scheme