Theoretical study of underpotential deposition of foreign metal atoms on Pt(111) single-crystal cluster surfaces

ABSTRACTWe present the structure and thermoelectric properties of the new quaternary selenides K1+xM4–2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22. The compounds K1+xM4-2xBi7+xSe15 (M= Sn, Pb) crystallize isostructural to A1+xPb4-2xSb7+xSe15 with A = K, Rb, while K1-xSn5-xBi11+xSe22 reveals a new structure type. In both structure types fragments of the Bi2Te3-type and the NaCl-type are connected to a three-dimensional anionic framework with K+ ions filled tunnels. The two structures vary by the size of the NaCl-type rods and are closely related to β-K2Bi8Se13 and K2.5Bi8.5Se14. The thermoelectric properties of K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22 were explored on single crystal and ingot samples. These compounds are narrow gap semiconductors and show n-type behavior with moderate Seebeck coefficients. They have very low thermal conductivity due to an extensive disorder of the metal atoms and possible “rattling” K+ ions.

Download Full-text

Strukturvarianten des MgCu2-Typs: Die Verbindungen Mg2Ni3P und Mg2Ni3As / Variants of the MgCu2 Type: The Compounds Mg2Ni3P and Mg2Ni3As

Zeitschrift für Naturforschung B ◽

10.1515/znb-1992-1002 ◽

1992 ◽

Vol 47 (10) ◽

pp. 1351-1354 ◽

Cited By ~ 7

Author(s):

Viktor Keimes ◽

Albrecht Mewis

Keyword(s):

Single Crystal ◽

Homogeneity Range ◽

Hexagonal Lattice ◽

Structure Type ◽

Type Structure ◽

X Ray ◽

Lattice Constants ◽

Metal Atoms ◽

Rhombohedral Symmetry

The compounds Mg2Ni3P and Mg2Ni3As were prepared by heating the elements. Their structures have been determined from single-crystal X-ray data. The structure of the phosphide is a rhombohedral ternary variant of the cubic Laves structure type MgCu2 (R 3̄ m; hexagonal lattice constants: a = 4.971(0) Å, c = 10.961(2) Å). The ordered substitution of one quarter of the metal atoms by phosphorus and the resulting shorter distances are responsible for the rhombohedral symmetry.The arsenide crystallizes in the MgCu2 type structure (Fd 3 m; a = 6.891(1)A, composition Mg2Ni3As) with a statistic distribution of the Ni and As atoms; the relevant homogeneity range extends from Mg2Ni2.9As1.1 to Mg2Ni3.5As0.5.

Download Full-text

Theoretical study of phase transitions and underpotential deposition on a liquid|solid interface

Journal of Electroanalytical Chemistry ◽

10.1016/s0022-0728(97)80057-5 ◽

1997 ◽

Vol 440 (1-2) ◽

pp. 201-210

Author(s):

A.A. Tarasenko ◽

L. Jastrabík

Keyword(s):

Phase Transitions ◽

Theoretical Study ◽

Underpotential Deposition ◽

Solid Interface

Download Full-text

Second hyperpolarizability of multimetallocenes [Cp–Mn–Cp] of Be, Mg and Ca

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633615500029 ◽

2015 ◽

Vol 14 (01) ◽

pp. 1550002 ◽

Cited By ~ 5

Author(s):

Kaushik Hatua ◽

Prasanta K. Nandi

Keyword(s):

Charge Transfer ◽

Theoretical Study ◽

Small Variation ◽

Cooperative Effect ◽

Second Hyperpolarizability ◽

Nlo Property ◽

Metal Atoms ◽

Bonding Interaction ◽

Charge Transfer Transitions ◽

The Difference

Multimetallocene complexes ( Cp – M n– Cp ) of Be , Mg and Ca have been considered for the theoretical study of static second hyperpolarizability using a number of DFT functionals. Owing to the cooperative effect in bonding, beryllium forms multiberyllocene complexes ( Cp – Be n– Cp ) which have sufficient thermal stability with respect to dissociation into neutral fragments up to n = 10. On the other hand, multimetallocene complexes of Mg and Ca are found to be stable for n ≤ 5 which may be due to the weaker covalent bonding interaction between the larger metal atoms. The rather small variation of linear and cubic polarizabilities of Cp – Be n– Cp complexes beyond n = 5 arises from the rather weaker charge transfer transitions. The difference in NLO property among the investigated metal complexes arises from the extent of charge transfer from the terminal metal atoms and the distance between them. The charge transfer at longer distances in the ground state of Mg and Ca complexes leads to more intense electronic transition — the spectroscopic parameters of which strongly favors the enhancement of second hyperpolarizability.

Download Full-text