Electronic Origin of the Structural Anomalies of Zinc and Cadmium

Wedig, Ulrich; Nuss, Hanne; Nuß, Jürgen; Jansen, Martin; Andrae, Dirk; Paulus, Beate; Kirfel, Α.; Weyrich, Wolf

doi:10.1002/zaac.201300091

Cited by 10 publications

(5 citation statements)

References 55 publications

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“…For Zn and Cd it has been found difficult to achieve simultaneously good agreement for structure, cohesive energy, and bulk modulus at the PBE, TS, and TS+SCS levels of theory, which can be achieved only by coupled-cluster calculations. 56 Here we want to examine the performance of the TS and TS/HI schemes for a class of intermetallic compounds known as Zintl phases, 57, 58 consisting of atoms with a large difference in electronegativity. The standard interpretation of the structure of Zintl phases is that due to the large electronegativity difference, electrons are transferred from the atoms with the lower electronegativity to those with higher electronegativity and that the anions form a sublattice with a structure similar to that of the isoelectronic neutral species.…”

Section: B Metals and Intermetallic Compoundsmentioning

confidence: 99%

Extending the applicability of the Tkatchenko-Scheffler dispersion correction via iterative Hirshfeld partitioning

Bučko

Lebègue²,

Ángyán³

et al. 2014

The Journal of Chemical Physics

195

190

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Recently we have demonstrated that the applicability of the Tkatchenko-Scheffler (TS) method for calculating dispersion corrections to density-functional theory can be extended to ionic systems if the Hirshfeld method for estimating effective volumes and charges of atoms in molecules or solids (AIM's) is replaced by its iterative variant [T. Bučko, S. Lebègue, J. Hafner, and J. Ángyán, J. Chem. Theory Comput. 9, 4293 (2013)]. The standard Hirshfeld method uses neutral atoms as a reference, whereas in the iterative Hirshfeld (HI) scheme the fractionally charged atomic reference states are determined self-consistently. We show that the HI method predicts more realistic AIM charges and that the TS/HI approach leads to polarizabilities and C6 dispersion coefficients in ionic or partially ionic systems which are, as expected, larger for anions than for cations (in contrast to the conventional TS method). For crystalline materials, the new algorithm predicts polarizabilities per unit cell in better agreement with the values derived from the Clausius-Mosotti equation. The applicability of the TS/HI method has been tested for a wide variety of molecular and solid-state systems. It is demonstrated that for systems dominated by covalent interactions and/or dispersion forces the TS/HI method leads to the same results as the conventional TS approach. The difference between the TS/HI and TS approaches increases with increasing ionicity. A detailed comparison is presented for isoelectronic series of octet compounds, layered crystals, complex intermetallic compounds, and hydrides, and for crystals built of molecules or containing molecular anions. It is demonstrated that only the TS/HI method leads to accurate results for systems where both electrostatic and dispersion interactions are important, as illustrated for Li-intercalated graphite and for molecular adsorption on the surfaces in ionic solids and in the cavities of zeolites.

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Section: B Metals and Intermetallic Compoundsmentioning

confidence: 99%

Extending the applicability of the Tkatchenko-Scheffler dispersion correction via iterative Hirshfeld partitioning

Bučko

Lebègue²,

Ángyán³

et al. 2014

The Journal of Chemical Physics

195

190

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“…They reported that the thermal motion of Zn shows a striking anisotropy as expressed by a ratio / of ≈ 2.6 at 500 K [1]. The electronic origin of the structural anomalies of zinc was studied by Wedig et al using experimental and theoretical calculations [2]. Their findings indicated that the anomalies of c/a ratio are caused by 4s-3d electron interactions rather than anisotropy in thermal expansion, and they suggested that the anomalous hcp structure of zinc results from a kinetic balancing of the valence electrons, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Their findings indicated that the anomalies of c/a ratio are caused by 4s-3d electron interactions rather than anisotropy in thermal expansion, and they suggested that the anomalous hcp structure of zinc results from a kinetic balancing of the valence electrons, i.e. through correlationmediated 4s-3d interactions [2].…”

Section: Introductionmentioning

confidence: 99%

Toward an Understanding of the Anisotropy in Hcp Zinc Metal: Total Scattering Structural Study Using Synchrotron-Based, Temperature-Dependent, X-Ray Pair Distribution Function Analysis

2024

JJP

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Among hexagonal close packing (hcp) metals, zinc has a non-ideal hcp structure due to a significantly increased axial ratio c/a. We studied the behavior of the ratio of lattice constants c/a and the ratio of thermal displacement parameters (U_33 / U_11) in the temperature range of 100-300 K, using the X-ray total scattering atomic pair distribution function (PDF) analysis over different refinement r-ranges. The temperature-dependent PDF analysis confirmed that the crystal structure of zinc has significant static distortion along the c-direction. The measured value of atomic displacement parameters of zinc showed a notable anisotropy as expressed by the ratio U_33 / U_11 of ≈ 2.2 at 100 K. The lattice parameter ratio c/a was slightly reduced at low temperatures but remained unusually large. The extrapolated value of the ratio c/a reached 1.832 at 0 K. The PDF refinements using the crystallographic model revealed that there are some local structure features in zinc that are not captured by the crystallographic model. On the other hand, our local structure refinement indicated a presence of local bond distortion along the z-direction that averaged out over wider r-range refinements with a large U_33 value. Keywords: Hcp anisotropy, Zinc metal, Total scattering, X-ray scattering, Pair distribution function. PACs numbers: 61.46.Df, 61.10.-i, 78.66.Hf, 61.46.-w.

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“…1−5 Cd has more localized d electrons (in a closed 4d shell) than other transition metals in the same period, leading to intriguing chemical and physical properties, such as low melting points and structural anomalies. 6 Cd's diagonal relationship with Tl in the periodic table inspired us to look for new compounds based on its moderate electronegativity, as well as for the possibility that it might form compounds based on Cd clusters or polymeric frameworks analogous to (Tl) n n− in NaTl. 7 Many Zintl-like 8 compounds are known for binary alkali-metal−Cd solid-state systems.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Among the late transition metals, cadmium (Cd) has been widely studied both experimentally and theoretically. Experimentally, it forms diverse, complex crystal structures ranging from NaCd 2 (Samson, 1962) and Cu 4 Cd 3 (Samson, 1967) to quasicrystals such as RE Cd ∼6 ( RE = rare earth). − Cd has more localized d electrons (in a closed 4d shell) than other transition metals in the same period, leading to intriguing chemical and physical properties, such as low melting points and structural anomalies . Cd’s diagonal relationship with Tl in the periodic table inspired us to look for new compounds based on its moderate electronegativity, as well as for the possibility that it might form compounds based on Cd clusters or polymeric frameworks analogous to (Tl) n n – in NaTl .…”

Section: Introductionmentioning

confidence: 99%

Composite Icosahedron/Cube Endohedral Clusters in Rh₂Cd₁₅

et al. 2016

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We present Rh2Cd15, the first binary compound in the Rh-Cd system. It is based on transition-metal-embedded (Rh@Cd11 and Rh@Cd12) endohedral Cd clusters that are single- and double-capped IC10 composite icosahedra/cubes. We demonstrate the structural connections between the clusters. On the basis of the analysis of atomic interactions and electron counting, 50 electrons per Rh2Cd15 is postulated to be the boundary between bonding and antibonding interactions. This understanding is supported by electronic structure calculations showing that the electron count for Rh2Cd15 (48 electrons per Rh2Cd15) is located close to a deep pseudogap in the electronic density of states at 50 electrons per formula unit, which we postulate is an important factor in determining the new compound's stability.

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Electronic Origin of the Structural Anomalies of Zinc and Cadmium

Cited by 10 publications

References 55 publications

Extending the applicability of the Tkatchenko-Scheffler dispersion correction via iterative Hirshfeld partitioning

Extending the applicability of the Tkatchenko-Scheffler dispersion correction via iterative Hirshfeld partitioning

Toward an Understanding of the Anisotropy in Hcp Zinc Metal: Total Scattering Structural Study Using Synchrotron-Based, Temperature-Dependent, X-Ray Pair Distribution Function Analysis

Composite Icosahedron/Cube Endohedral Clusters in Rh₂Cd₁₅

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Electronic Origin of the Structural Anomalies of Zinc and Cadmium

Cited by 10 publications

References 55 publications

Extending the applicability of the Tkatchenko-Scheffler dispersion correction via iterative Hirshfeld partitioning

Extending the applicability of the Tkatchenko-Scheffler dispersion correction via iterative Hirshfeld partitioning

Toward an Understanding of the Anisotropy in Hcp Zinc Metal: Total Scattering Structural Study Using Synchrotron-Based, Temperature-Dependent, X-Ray Pair Distribution Function Analysis

Composite Icosahedron/Cube Endohedral Clusters in Rh2Cd15

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Composite Icosahedron/Cube Endohedral Clusters in Rh₂Cd₁₅