Polarity-extended 8 − <i>N</i><sup>eff</sup> rule for semiconducting main-group compounds with the TiNiSi-type of crystal structure

Freccero, Riccardo; Grin, Yu.; Wagner, Frank R.

doi:10.1039/d3dt00621b

Cited by 7 publications

(3 citation statements)

References 42 publications

(74 reference statements)

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“…[22] In fact, beside the silicon atoms, which are the main contributors to the electronic population of these basins, several cations contribute as well, but with minor amounts, i. e. in a solid, such basin represents rather a strongly polar multi-atomic bond. [23] One consequence of this are the effective charges of the cations (Figure 3), which are significantly lower as the values of + 1 (K) and + 2 (Ba) in the Zintl-Klemm concept. Furthermore, the populations of these multiatomic bond basins are essentially larger than two electrons expected from the Zintl counting scheme.…”

Section: Resultsmentioning

confidence: 96%

K₂BaSi₄: Zintl Concept in Position Space

Grin¹,

Sichevych

Akselrud³

et al. 2023

Zeitschrift anorg allge chemie

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The Zintl phase K2BaSi4 has been synthesized from the mixture of precursors KSi and BaSi2. The crystal structure of K2BaSi4 was elucidated from X‐ray powder diffraction data: Pearson symbol oP28, space group Pbcm, a=9.4950(1), b=9.2392(1), c=9.9025(1) Å. The main building block of the crystal structure are tetrahedral anions Si44–. Analysis of chemical bonding for K2BaSi4 and its chemical analogs – molecular H4Si4 and solid state K4Si4 employing the electron localizability approach reveals the basic agreement with the Zintl model in terms of number of basins for Si−Si bonds and lone pairs at Si atoms, as well as the charge transfer direction. The populations of the bond and ‘lone‐pair’ basins agree with the Zintl count for molecular species and deviate strongly for the solids, in particular, while the ‘lone‐pair’ basins are over‐populated, the bond basins are essentially under‐populated. The topology of the calculated electron density and electron‐localizability indicator is very sensitive toward the interatomic distances and angles in the Si44− anion.

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Section: Resultsmentioning

confidence: 96%

K₂BaSi₄: Zintl Concept in Position Space

Grin¹,

Sichevych

Akselrud³

et al. 2023

Zeitschrift anorg allge chemie

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“…In a polar covalent framework, this notion is challenged, and coordination numbers larger than 4 are observed, e.g., in certain silicates where CN (Si) = 6, or e.g., CaF 2 and TiNiSi type 8-valence electron main-group compounds with polar-covalent coordination numbers of 8 to 10. In these latter cases, the fractional covalent character of each bond, i.e., its fractional covalent bond population being smaller than 2 electrons, was shown to still yield local octet-rule fulfillment even for this type of bonding scenario in the framework of a polarity-extended 8– N eff rule …”

Section: Introductionmentioning

confidence: 99%

Topological Octet-Rule Implementation for Deltahedral Boron Hydrides and Related Zintl Clusters of the Main-Group Elements: Flexible Octet-Rule Fulfillment by Mixed 2- and 3-Center Fractional Bonding Scenarios

Wagner,

Grin

2024

Inorg. Chem.

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In the large class of main-group Zintl phases, the octet rule plays a key role for the polyanions following the pseudoatom concept and the 8−N rule, such that a unique correspondence between atomic partial structure and its electron count results. In the conceptual framework of the Wade's type of clusters the relations to the octet rule are less obvious, and its structural implications are not clear. For this purpose, a topological implementation of the octet rule (TORI) within a delocalized bonding scenario is introduced. It is based on the average topology of the deltahedral cluster skeletons and the octet rule applied to delocalized fractional 2-and 3-center bond distributions. For a given skeletal electron pair count SEP, TORI yields values (t toc , y toc ) similar to the styx approach. Two hierarchically different types of octet-rule fulfillment are identified, the cluster-wise and the local one. The local octet-rule fulfillment always implies the cluster-wise one, while the converse is not true. Deltahedral clusters with different skeletal shapes but the same Wade's SEP count can be distinguished with respect to different octet-rule fulfillment. The TORI approach opens a perspective to compare Zintl phases containing Wade-type clusters with those containing 8−N type of partial structures on the basis of octet-rule implications. The main difference to the 8−N type of partial structures identified is the more flexible way of octet-rule fulfillment in the Wade's type clusters, which does not prevent them from realizing the same cluster topology with different SEP counts. The TORI approach works with delocalized fractional bonds and is consistent with the concept of PSEPT; it just adds an additional facet.

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“…The phase with the original AlB 2 -type structure was supposed to be either a high temperature modification of EuGa 2 , [16] or to be stabilized by (non-metallic) impurities. [17] In the course of study on the bonding in intermetallic compounds with structures motifs being derivatives of the AlB 2 type, [21,22] i. e. digallides of the rare-earth metals, [23] the aim of this work was the detailed structural and bonding characterization of the hexagonal europium digallide.…”

Section: Introductionmentioning

confidence: 99%

On europium digallides

Sichevych¹,

Ramlau²,

Schnelle³

et al. 2023

Zeitschrift anorg allge chemie

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The europium gallide Eu1‐xGa2+3x (x is between 0.06 and 0.07) has been synthesized and its crystal structure has been refined from single crystal X‐ray diffraction data. Eu1‐xGa2+3x crystallizes with hexagonal structure related to the AlB2‐type (space group P6/mmm, a=4.354 Å, c=4.485 Å). The structure refinement finished with R(F)=0.015 for 1603 reflections revealing a defect occupation of the Eu position (93 %) and additional Ga position, yielding the non‐integer element ratio. From magnetic susceptibility measurements, EuGa2 and Eu1‐xGa2+3x phases show the 4f 7 (Eu+2) oxidation state. The analysis of effective atomic charges within the Quantum Theory of Atoms in Molecules reveals the formation of four‐bonded Ga species with low electron demand (in comparison to the three‐bonded in AlB2‐type and four‐bonded in the KHg2‐type structures) and shows, that Eu1‐xGa2+3x represents a new way of stabilizing intermetallic structures formed at valence electron concentration, which does not allow to apply Zintl‐like electron counting.

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Polarity-extended 8 − N^eff rule for semiconducting main-group compounds with the TiNiSi-type of crystal structure

Abstract: For semiconducting main-group compounds of the TiNiSi-type of structure quantum-chemically obtained polar-covalent bonding data in position-space are consistently transferred to and analyzed within the framework of the polarity-extended 8 − Neff rule.

Cited by 7 publications

References 42 publications

K₂BaSi₄: Zintl Concept in Position Space

K₂BaSi₄: Zintl Concept in Position Space

Topological Octet-Rule Implementation for Deltahedral Boron Hydrides and Related Zintl Clusters of the Main-Group Elements: Flexible Octet-Rule Fulfillment by Mixed 2- and 3-Center Fractional Bonding Scenarios

On europium digallides

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Polarity-extended 8 − Neff rule for semiconducting main-group compounds with the TiNiSi-type of crystal structure

Abstract: For semiconducting main-group compounds of the TiNiSi-type of structure quantum-chemically obtained polar-covalent bonding data in position-space are consistently transferred to and analyzed within the framework of the polarity-extended 8 − Neff rule.

Cited by 7 publications

References 42 publications

K2BaSi4: Zintl Concept in Position Space

K2BaSi4: Zintl Concept in Position Space

Topological Octet-Rule Implementation for Deltahedral Boron Hydrides and Related Zintl Clusters of the Main-Group Elements: Flexible Octet-Rule Fulfillment by Mixed 2- and 3-Center Fractional Bonding Scenarios

On europium digallides

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Polarity-extended 8 − N^eff rule for semiconducting main-group compounds with the TiNiSi-type of crystal structure

K₂BaSi₄: Zintl Concept in Position Space

K₂BaSi₄: Zintl Concept in Position Space