# Electronic structure of the bulk and layers of the alkaline earths (Be-Ba)

TL;DR: In this article, the results of electronic structure calculations for the bulk and layers of the alkaline earths (Be-Ba) were made using the linearized muffin-tin orbital method within the local density approximation.

Abstract: We report the results of electronic structure calculations for the bulk and layers of the alkaline earths (Be-Ba) made using the linearized muffin-tin orbital method within the local density approximation. In agreement with experiments, bulk calcium and strontium are found to undergo a metal-semi-metal transition under compression, whereas for each of these elements a single (100) layer is found to have vanishing density of states at the Fermi energy at normal pressure. A layer of Ba, on the other hand, exhibits a similar behaviour under expansion. As compared to the bond length for the bulk, there is an expansion for a single layer in all of the cases. This expansion is large for Mg, which is consistent with the large bond length of the Mg dimer. The binding energy for a single layer is close to its value for dimers but it increases by a large amount for three layers. These results are discussed in terms of the changes in the s-p/d hybridization with the reduction in the coordination, and its importance for understanding the properties of clusters of transition metals.

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TL;DR: In this paper, the bulk and surface properties of hexagonal-close-packed beryllium and magnesium were calculated with two forms of the exchange-correlation functional. And the results of the two metals calculated within the generalized gradient approximation (GGA) are closer to the measured ones than the local density approximation (LDA) results are.

Abstract: Density functional theory and a plane-wave basis pseudopotential technique are applied to calculate the bulk and the (0001) surface properties of hexagonal-close-packed (hcp) beryllium and magnesium. The calculations were performed with two forms of the exchange-correlation functional. The bulk properties of the two metals calculated within the generalized gradient approximation (GGA) are closer to the measured ones than the local density approximation (LDA) results are. The GGA also provides results for lattice relaxations, work functions, and surface energies which are in a better agreement with experimental values than the LDA results are. The changes of surface energy and work function with slab thickness varying between 3 and 13 atomic layers were considered. Quantum-size effects did not influence the calculated work function and surface energies significantly.

92 citations

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TL;DR: In this paper, the Mendeleev number was used to classify quasicrystals into four structural classes based on the nature of the bond orbital of the large atom with four associated related crystal structures.

Abstract: Quasicrystal-forming ability is considered from the viewpoint of Pettifor maps, where a single phenomenological coordinate, the Mendeleev number, captures the bonding characteristics of elements in forming intermetallics. By considering the largest sized atom as the most important constituent, it is shown that most known ternary and quaternary quasicrystals can be treated as pseudo-binary intermetallics. This also results in a classification of quasicrystals into four structural classes based on the nature of the bond orbital – s, p, d or f – of the large atom with four associated related crystal structures. A colour scheme is introduced to indicate preferences for two types of sites. We propose a new classification of quasicrystals as centred on Li, Mg, Al, Ga, Ca, Sc, Y, Ti, Zr, Hf and rare earth elements, as they are the largest atoms in the constituent quasicrystals in contrast to the conventional classification based on majority species.

30 citations

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TL;DR: In this paper, density functional theory and a plane-wave basis pseudopotential technique are applied to calculate relaxations of the first three interlayer spacings at the (0001) surface of thick Be and Mg slabs.

Abstract: Density functional theory and a plane-wave basis pseudopotential technique is applied to calculate relaxations of the first three interlayer spacings at the (0001) surface of thick Be and Mg slabs. For both metals the calculated outward relaxation of the topmost layer and small relaxations of the deeper layers are in good agreement with experiment and previous calculations. The calculated multilayer relaxations are analysed in terms of the electron charge density profile perpendicular to the surface which shows an oscillatory character with a period consistent with the long-range Friedel oscillations. Our results provide arguments for the generalization of the physical model relating the origin of multilayer relaxation to Friedel oscillations at the bulk truncated surface.

13 citations

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01 Apr 2005-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms

TL;DR: In this paper, high-resolution Auger-electron spectroscopy has been applied to the interaction of swift heavy ions with atomically clean metallic solids, extracting ion-track potentials and also electron temperatures inside ion tracks.

Abstract: High resolution Auger-electron spectroscopy has been applied to the interaction of swift heavy ions with atomically clean metallic solids. Spectra have been taken for fast projectile electrons and for charge-state equilibrated ions at normal incidence on microcrystalline beryllium samples, Al(1 0 0) single crystals and several metallic glasses (Al 87 La 7 Ni 5 Zr 1 , Ni 78 B 14 Si 8 , Co 66 Si 16 B 12 Fe 4 Mo 2 ). From the energy shift and from the Auger-line width we have extracted ion-track potentials and also electron temperatures inside ion tracks. A first determination of the angular distribution of multiple-ionization lines is presented as well.

10 citations

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TL;DR: The out-of-equilibrium transport properties of Anderson insulators exhibit many glassy features such as slow relaxation, slow approach to a steady state, ageing, and other memory effects as mentioned in this paper.

Abstract: The out-of-equilibrium transport properties of Anderson insulators exhibit many glassy features such as slow relaxation, slow approach to a steady state, ageing, and other memory effects. These non-equilibrium features were theoretically anticipated and are believed to result from the interplay between disorder and interactions. Here we review the field-effect experiments that establish the generic nature of electron glasses. It is pointed out that the common feature to all systems that exhibit the characteristic electron-glass properties is their relatively high carrier concentration. Experiments performed as a function of the carrier concentration indicate that below a critical value, the relaxation time becomes very short. It is suggested that this may be the reason why lightly doped semiconductors do not exhibit intrinsic electron-glass effects. The possible connection between the Coulomb gap and the memory dip is discussed.

7 citations

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TL;DR: In this paper, the Hartree and Hartree-Fock equations are applied to a uniform electron gas, where the exchange and correlation portions of the chemical potential of the gas are used as additional effective potentials.

Abstract: From a theory of Hohenberg and Kohn, approximation methods for treating an inhomogeneous system of interacting electrons are developed. These methods are exact for systems of slowly varying or high density. For the ground state, they lead to self-consistent equations analogous to the Hartree and Hartree-Fock equations, respectively. In these equations the exchange and correlation portions of the chemical potential of a uniform electron gas appear as additional effective potentials. (The exchange portion of our effective potential differs from that due to Slater by a factor of $\frac{2}{3}$.) Electronic systems at finite temperatures and in magnetic fields are also treated by similar methods. An appendix deals with a further correction for systems with short-wavelength density oscillations.

42,177 citations

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TL;DR: In this article, the ground state of an interacting electron gas in an external potential was investigated and it was proved that there exists a universal functional of the density, called F[n(mathrm{r})], independent of the potential of the electron gas.

Abstract: This paper deals with the ground state of an interacting electron gas in an external potential $v(\mathrm{r})$. It is proved that there exists a universal functional of the density, $F[n(\mathrm{r})]$, independent of $v(\mathrm{r})$, such that the expression $E\ensuremath{\equiv}\ensuremath{\int}v(\mathrm{r})n(\mathrm{r})d\mathrm{r}+F[n(\mathrm{r})]$ has as its minimum value the correct ground-state energy associated with $v(\mathrm{r})$. The functional $F[n(\mathrm{r})]$ is then discussed for two situations: (1) $n(\mathrm{r})={n}_{0}+\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{n}(\mathrm{r})$, $\frac{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{n}}{{n}_{0}}\ensuremath{\ll}1$, and (2) $n(\mathrm{r})=\ensuremath{\phi}(\frac{\mathrm{r}}{{r}_{0}})$ with $\ensuremath{\phi}$ arbitrary and ${r}_{0}\ensuremath{\rightarrow}\ensuremath{\infty}$. In both cases $F$ can be expressed entirely in terms of the correlation energy and linear and higher order electronic polarizabilities of a uniform electron gas. This approach also sheds some light on generalized Thomas-Fermi methods and their limitations. Some new extensions of these methods are presented.

33,880 citations

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TL;DR: In this article, a spin dependent one-electron potential pertinent to ground state properties is obtained from calculations of the total energy per electron made with a 'bubble' (or random phase) type of dielectric function.

Abstract: The local density theory is developed by Hohenberg, Kohn and Sham is extended to the spin polarized case. A spin dependent one- electron potential pertinent to ground state properties is obtained from calculations of the total energy per electron made with a 'bubble' (or random phase) type of dielectric function. The potential is found to be well represented by an analytic expression corresponding to a shifted and rescaled spin dependent Slater potential. To test this potential the momentum dependent spin susceptibility of an electron gas is calculated. The results compare favourably with available information from other calculations and from experiment. The potential obtained in this paper should be useful for split band calculations of magnetic materials.

3,587 citations

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TL;DR: In this paper, the authors survey the local density functional formalism and some of its applications and discuss the reasons for the successes and failures of the local-density approximation and some modifications.

Abstract: A scheme that reduces the calculations of ground-state properties of systems of interacting particles exactly to the solution of single-particle Hartree-type equations has obvious advantages. It is not surprising, then, that the density functional formalism, which provides a way of doing this, has received much attention in the past two decades. The quality of the energy surfaces calculated using a simple local-density approximation for exchange and correlation exceeds by far the original expectations. In this work, the authors survey the formalism and some of its applications (in particular to atoms and small molecules) and discuss the reasons for the successes and failures of the local-density approximation and some of its modifications.

3,106 citations