The energy-versus-volume curve of the spin-density wave (SDW) in body-centred-cubic Cr is calculated with the density functional theory/full-potential linearized augmented plane wave (DFT/FLAPW) method using the generalized gradient approximation (GGA). The predicted ground state is not the SDW, in contrast to an earlier FLAPW calculation. A conjecture is formulated that the widely varying results of the local density approximation (LDA) and GGA - and of different solution methods - can be scaled by the size of the calculated moment. As a consequence, experimentally relevant properties of the SDW can be calculated by tuning the moment. The implications of these results for the ability of DFT to describe Cr are discussed.

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The magnetic hyperfine field and electric-field gradient at isolated lanthanide impurities in an Fe host lattice are calculated from first principles, allowing for the first time a qualitative and quantitative understanding of an experimental data set collected over the past 40 years. It is demonstrated that the common Local Density Approximation leads to quantitatively and qualitatively wrong results, while the LDA+U method performs much better. In order to avoid pitfalls inherent to the LDA+U method, a careful strategy had to be used, which will be described in detail. The lanthanide 4f spin moment is found to couple antiferromagnetically to the magnetization of the Fe lattice, in agreement with the model of Campbell and Brooks. There is strong evidence for a delocalization/localization transition that is shifted from Ce to at least Pr and maybe further up to Sm. This shift is interpreted in terms of the effective pressure felt by lanthanides in Fe. Implications for resolving ambiguities in the determination of delocalization in pure lanthanide metals under pressure are discussed. For the localized lanthanides, Yb is shown to be divalent in this host lattice, while all others are trivalent (including Eu, the case of Tm is undecided). The completely filled and well-bound 5p shell of the lanthanides is shown to have a major and unexpected influence on the dipolar hyperfine field and on the electric-field gradient, a feature that can be explained by their 1/r^3 dependence. An extrapolation to actinides suggests that the same is true for the actinide 6p shell. The case of free lanthanide atoms is discussed as well.Comment: 17 pages, 14 figure

We determine the temperature dependence of the electric-field gradient in hcp-Cd from first principles. The calculations are based on the ab initio determination of the phonon density of states spectrum of the solid. Using only moderate accuracy requirements, the temperature dependence of the electric-field gradient in hcp-Cd is reasonably well reproduced. The origin of its peculiar T-3/2 dependence is discussed

We present a comparison between accurate ab initio calculations and a high-quality experimental data set (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002) of electric-field gradients of Cd at different sites on Ni, Cu, Pd, and Ag surfaces. Experiments found a systematic rule to assign surface sites on (100) and (111) surfaces based on the main component of the electric-field gradient, a rule that does not work for (110) surfaces. Our calculations show that this particular rule is a manifestation of a more general underlying systematic behavior. When looked upon from this point of view, (100), (111) and (110) surfaces behave in precisely the same way. The physical mechanism behind the systematics of the EFG for other 5sp impurities ͑Cd-Ba͒ at different fcc surfaces sites is revealed, showing in a natural way why the first half of the 5p elements shows a coordination dependence that is opposite with respect to the second half.