Stabilizing heteroatom-centered 16-vertex group 11 tetrahedral architectures Bonding and structural considerations toward versatile endohedral species

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[M16Ni24(CO)(40)](4-) Coinage Metal Tetrahedral Superatoms as Useful Building Blocks Related to Pyramidal Au-20 Clusters (M = Cu, Ag, Au). Electronic and Bonding Properties from Relativistic DFT Calculations

International audienceCharacterization of the tetrahedral Au-20 structure in the gas phase remains a major landmark in gold cluster chemistry, where further efforts to stabilize this bare 20-electron superatom in solution to extend and understand its chemistry have failed so far. Here, we account for the structural, electronic, and bonding properties of [M16Ni24(CO)(40)](4-) (M = Cu, Ag, Au) observed in solution for gold and silver. Our results show a direct electronic relationship with Au20, owing that such species share a common tetrahedral [M-16](4-) central core with a 1S(21)P(61)D(10)2S(2) jellium configuration. In the case of Au-20, the [Au-16](4-) core is capped by four Au+ ions, whereas in [M(16N)i(24)(CO)(40)](4-) it is capped by four Ni-6(CO)(10) units. In both cases, the capping entities are a full part of the superatom entity, where it appears that the free (uncapped) [M-16](4-) species must be capped for further stabilization. It follows that the Ni-6(CO)(10) units in [M16Ni24(CO)(40)](4-) should not be considered as external ligands as their bonding with the [M-16](4-) core is mainly associated with a delocalization of the 20 jellium electrons onto the Ni atoms. Thus, the [M16Ni24(CO)(40)](4-) species can be seen as the solution version of tetrahedral M-20 clusters, encouraging experimental efforts to further develop the chemistry of such complexes as M(111) finite surface section structures, with M = Ag and Au and, particularly promising, with M = Cu. Furthermore, optical properties were simulated to assist future experimental characterization

Symmetry lowering by cage doping in spherical superatoms Evaluation of electronic and optical properties of 18-electron W@Au12Ptn (n=0-4) superatomic clusters from relativistic DFT calculations

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Potential to stabilize 16-vertex tetrahedral coinage-metal cluster architectures related to Au-20

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Coinage Metal Superatomic Cores: Insights into Their Intrinsic Stability and Optical Properties from Relativistic DFT Calculations

International audienceCoinage-metal atomically precise nanoclusters are made of a well-defined metallic core embedded in a ligand-protecting outer shell. Whereas gold derivatives are particularly well documented, examples of silver nanoclusters are somewhat limited and copper species remain particularly scare. Our DFT relativistic calculations on superatomic metallic cores indicate that copper species are almost as stable as gold clusters and more stable than their silver counterparts. Thus, for silver superatomic cores, the role of the stabilizing ligands is more crucial in the stabilization of the overall structure, in comparison to copper and gold. Hence, the chemistry of the earlier counterparts of gold, especially copper, should grow quickly with at least characterizations of species related to that found in the heavier elements in the triad, which requires tackling synthetic challenges. Time-dependent (TD)-DFT calculations show that with an increase of the cluster core nuclearity, the absorption bands are redshifted, allowing us to differentiate between the clusters types. Moreover, the optical properties of the silver cores are fairly different from that of their Cu and Au relatives

[M₁₆Ni₂₄(CO)₄₀]^4–: Coinage Metal Tetrahedral Superatoms as Useful Building Blocks Related to Pyramidal Au₂₀ Clusters (M = Cu, Ag, Au). Electronic and Bonding Properties from Relativistic DFT Calculations

Characterization of the tetrahedral Au₂₀ structure in the gas phase remains a major landmark in gold cluster chemistry, where further efforts to stabilize this bare 20-electron superatom in solution to extend and understand its chemistry have failed so far. Here, we account for the structural, electronic, and bonding properties of [M₁₆Ni₂₄(CO)₄₀]^4– (M = Cu, Ag, Au) observed in solution for gold and silver. Our results show a direct electronic relationship with Au₂₀, owing that such species share a common tetrahedral [M₁₆]^4– central core with a 1S²1P⁶1D¹⁰2S² jellium configuration. In the case of Au₂₀, the [Au₁₆]^4– core is capped by four Au⁺ ions, whereas in [M₁₆Ni₂₄(CO)₄₀]^4– it is capped by four Ni₆(CO)₁₀ units. In both cases, the capping entities are a full part of the superatom entity, where it appears that the free (uncapped) [M₁₆]^4– species must be capped for further stabilization. It follows that the Ni₆(CO)₁₀ units in [M₁₆Ni₂₄(CO)₄₀]^4– should not be considered as external ligands as their bonding with the [M₁₆]^4– core is mainly associated with a delocalization of the 20 jellium electrons onto the Ni atoms. Thus, the [M₁₆Ni₂₄(CO)₄₀]^4– species can be seen as the solution version of tetrahedral M₂₀ clusters, encouraging experimental efforts to further develop the chemistry of such complexes as M(111) finite surface section structures, with M = Ag and Au and, particularly promising, with M = Cu. Furthermore, optical properties were simulated to assist future experimental characterization

Evidence of the thermo-electric Thomson effect and influence on the program conditions and cell optimization in phase-change memory cells

\u3cp\u3eWe present physical and electrical evidence of the Thomson thermo-electric effect in line-type phase-change memory cells. This causes a shift of the molten zone during RESET programming towards the anode contact, and as a consequence the phase change material (PCM) design at the contact area has a significant influence on the program conditions. First statistical studies showed a reduction of minimum Reset currents by ∼55% and Set voltages by ∼28% when PCM extensions around the anode are used instead of fine line contacts. This Thomson effect remains important with further cell scaling.\u3c/p\u3