scholarly journals Differences in two-dimensional crystal structures: Racemic and enantiopure heptahelicene on Cu(111)

2004 ◽  
Vol 2 ◽  
pp. 136-140 ◽  
Author(s):  
Karl-Heinz Ernst ◽  
Manfred Parschau ◽  
Roman Fasel
2021 ◽  
pp. 113336
Author(s):  
Tatiana Latychevskaia ◽  
Recep Zan ◽  
Sergey Morozov ◽  
Kostya S. Novoselov

2009 ◽  
Vol 65 (3) ◽  
pp. 300-307 ◽  
Author(s):  
G. D. Ilyushin ◽  
V. A. Blatov

A combinatorial topological analysis is carried out by means of the program package TOPOS4.0 [Blatov (2006), IUCr Comput. Commun. Newsl. 7, 4–38] and the matrix self-assembly is modeled for crystal structures of the ZrZn22 family (space group Fd\bar 3m, Pearson code cF184), including the compounds with superstructural ordering. A number of strict rules are proposed to model the crystal structures of intermetallics as a network of cluster precursors. According to these rules the self-assembly of the ZrZn22-like structures was considered within the hierarchical scheme: primary polyhedral cluster → zero-dimensional nanocluster precursor → one-dimensional primary chain → two-dimensional microlayer → three-dimensional microframework (three-dimensional supraprecursor). The suprapolyhedral cluster precursor AB 2 X 37 of diameter ∼ 12 Å and volume ∼ 350 Å3 consists of three polyhedra (one AX 16 of the \bar 43m point symmetry and two regular icosahedra BX 12 of the \bar 3m point symmetry); the packing of the clusters determines the translations in the resulting crystal structure. A novel topological type of the two-dimensional crystal-forming 4,4-coordinated binodal net AB 2, with the Schläfli symbols 3636 and 3366 for nodes A and B, is discovered. It is shown that the ZrZn22 superstructures are formed by substituting some atoms in the cluster precursors. Computer analysis of the CRYSTMET and ICSD databases shows that the cluster AB 2 X 37 occurs in 111 intermetallics belonging to 28 structure types.


Procedures are outlined for generation of crystal structures of primary amide molecules by constructing the possible ways in which the molecules may pack. For each given one- or two-dimensional hydrogen-bonded array, ensembles of three-dimensional crystal structures are generated by considering the possible ways in which the arrays may be juxtaposed. Observed and generated hypothetical molecular arrangements are analysed to highlight both favourable and unfavourable features, par­ticularly in terms of close packing principles, the size and shape of the molecule, van der Waals and Coulomb interactions and N-H ∙ ∙ ∙ O bonding geometry.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shota Ono

AbstractSome of the three-dimensional (3D) crystal structures are constructed by stacking two-dimensional (2D) layers. To study whether this geometric concept, i.e., using 2D layers as building blocks for 3D structures, can be applied to computational materials design, we theoretically investigate the dynamical stability of copper-based compounds CuX (a metallic element X) in the B$$_h$$ h and L1$$_1$$ 1 structures constructed from the buckled honeycomb (BHC) structure and in the B2 and L1$$_0$$ 0 structures constructed from the buckled square (BSQ) structure. We demonstrate that (i) if CuX in the BHC structure is dynamically stable, those in the B$$_h$$ h and L1$$_1$$ 1 structures are also stable. Using molecular dynamics simulations, we particularly show that CuAu in the B$$_h$$ h and L1$$_1$$ 1 structures withstand temperatures as high as 1000 K. Although the interrelationship of the metastability between the BSQ and the 3D structures (B2 and L1$$_0$$ 0 ) is not clear, we find that (ii) if CuX in the B2 (L1$$_0$$ 0 ) structure is dynamically stable, that in the L1$$_0$$ 0 (B2) is unstable. This is rationalized by the tetragonal Bain path calculations.


2001 ◽  
Vol 34 (5) ◽  
pp. 658-660 ◽  
Author(s):  
Plinio Delatorre ◽  
Walter Filgueira de Azevedo Jr

The simulations presented here are based on the programMathematicaas a tool to present electron density maps of two-dimensional crystal structures. The models give further insights into the relationship between the thermal displacement parameters and the quality of the electron density maps. Furthermore, users can readily test the effects of several crystallographic parameters on the electron density maps, such as, the number of reflections, the thermal displacement parameters and the unit-cell dimensions.


2003 ◽  
Vol 3 (4) ◽  
pp. 453-465 ◽  
Author(s):  
Scott W. Gordon-Wylie ◽  
George R. Clark

2002 ◽  
Vol 82 (5) ◽  
pp. 2700-2708 ◽  
Author(s):  
Alexander S. Solodukhin ◽  
Heather L. Caldwell ◽  
Julianne J. Sando ◽  
Robert H. Kretsinger

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