scholarly journals Детерминизм локального атомного упорядочения в монослоях золота в формировании их электронной структуры

2022 ◽  
Vol 64 (3) ◽  
pp. 303
Author(s):  
В.Л. Карбовский ◽  
А.А. Романский ◽  
Л.И. Карбовская ◽  
В.В. Стонис

The total and partial densities of electronic states of gold monolayer structures of different symmetry are calculated by the quantum mechanical calculations methods in the DFT approximation. It is shown that the first coordination sphere is determinant in the formation of the fine structure and the extent of the valence bands of the monolayer gold structures under study. The peaks splitting of the TDOS curve, which leads to its finer structure, is influenced not only by the lengths of interatomic bonds but also by the mutual arrangement of atoms. The influence of long-range interactions on the electronic structure of gold monolayers has been established. For example, for the (110) plane, a change in the atomic ordering in the third coordination sphere as a result of the introduction of a vacancy leads to noticeable changes in the TDOS curve, which indicates either a significant role of the atoms of the third coordination sphere or a significant redistribution of the interaction of d-orbitals of different symmetries of close neighbours. A correlation between the packing density, as well as the number of neighbours in the first coordination sphere, and the width of the energy band of gold monolayers has been established.

2005 ◽  
Vol 61 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Alla Arakcheeva ◽  
Gervais Chapuis ◽  
Vâclav Petricek ◽  
Vladimir Morozov

The incommensurate palmierite-like structure of β-K5Yb(MoO4)4, potassium ytterbium tetramolydate, has been refined in the (3 + 1)-dimensional monoclinic superspace group X2/m(0ρ0)00, with X = [0 0 0 0; ½ ½ 0 0; 0 0 ½ ½; ½ ½ ½ ½] and the unit-cell parameters a = 10.4054 (16), b = 6.1157 (12), c = 19.7751 (18) Å, β = 136.625 (10)°; q = 0.6354 (30)b*. The occupations of the K and Yb atomic positions are described by crenel functions. The structure model reveals a balanced interaction between the atoms of the first and second coordination spheres. It is shown that the third coordination sphere should not be neglected in studies of modulated structures. The ordering of the K and Yb atoms appears to be the driving force for the modulation of all the other atoms.


2015 ◽  
Vol 17 (5) ◽  
pp. 2917-2934 ◽  
Author(s):  
Eva Zurek ◽  
Wojciech Grochala

The role of quantum mechanical calculations in understanding and predicting the behavior of matter at extreme pressures is discussed in this feature contribution.


2014 ◽  
Vol 998-999 ◽  
pp. 124-127 ◽  
Author(s):  
Chang Ke Tian ◽  
Ai Ping Fu ◽  
Cheng Yan Zhao ◽  
Feng Hui Tian ◽  
Yun Bo Duan ◽  
...  

Quantum mechanical calculations have been performed to study the equilibrium among the key intermediates (iminium ion, oxazolidione, and enamine) in the proline-catalyzed reactions under base-free and base-present conditions. The results confirmed that the tautomeric equilibrium among these species can be tuned by the basic additives. The computations satisfactorily rationalized the experimental observations and provide a clue on how to stabilize the enamine intermediates.


2000 ◽  
Vol 72 (12) ◽  
pp. 2319-2332 ◽  
Author(s):  
Helmut Schwarz ◽  
Detlef Schröder

Concepts for the activation of methane are derived from ion-molecule reactions of mass-selected, ground-state transition-metal cations M+. Elementary steps of industrially important processes are uncovered (e.g., oxygenation of methane or its coupling with carbon dioxide). In addition, the implications of the electronic structures of M(CH2)+ complexes for their reactions with nucleophiles are discussed, and the crucial role of contemporary quantum mechanical calculations in the elucidation of mechanistic details is emphasized.


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