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Wyświetlanie 1-2 z 2
Tytuł:
Crystal Structure Prediction and Charge Density Distribution of Highly Energetic Dimethylnitraminotetrazole: a First Step for the Design of High Energy Density Materials
Autorzy:
Arputharaj, D. S.
Srinivasan, P.
Asthana, S. N.
Pawar, R. B.
Kumaradhas, P.
Powiązania:
https://bibliotekanauki.pl/articles/358205.pdf
Data publikacji:
2012
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
energetic materials
crystal structure prediction
charge density analysis
atoms in molecules
electrostatic potential
Opis:
The crystal structure of dimethylnitraminotetrazole has been predicted, based on systematically searching for densely packed structures within common organic crystal coordination types, followed by lattice energy minimization. The predicted crystal structures almost match the reported crystal structure determined by X-ray diffraction analysis. To understand the effect of the initial molecular geometry on the crystal packing, the crystal structure simulation was carried out for molecules taken from different environments, such as the X-ray structure (crystal field) and also from ab initiocalculations (gas phase). The predicted crystal structures from both environments are very similar to the reported X-ray structure with a maximum deviation of 4.5%. The crystal density predicted from both methods is close to that reported. The bond topological, energetic and electrostatic properties of the isolated molecule from the predicted crystal structure have been determined using Bader's theory of atoms in molecules. The bond topological characterization reveals that the C-N bond is the weakest bond in the molecule. A large electronegative potential is found in the vicinity of the NO2group and the nitrogen-rich region of the tetrazole ring; these are probably the reactive sites of this molecule.
Źródło:
Central European Journal of Energetic Materials; 2012, 9, 3; 201-217
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Borowce jako centra kwasów Lewisa w oddziaływaniach międzycząsteczkowych : porównanie z wiązaniami wodorowymi
Triels as centers of Lewis acids in intermolecular interactions : comparison with hydrogen bonds
Autorzy:
Grabowski, S. J.
Powiązania:
https://bibliotekanauki.pl/articles/172397.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
wiązanie wodorowe
wiązanie borowcowe
potencjał elektrostatyczny
dziura σ
dziura π
przesunięcie ładunku elektronowego
struktury krystaliczne
hydrogen bond
triel bond
electrostatic potential
σ-hole
π-hole
electron charge shift
crystal structures
Opis:
The triel bonds are analyzed and compared with the hydrogen bond interaction. The triel bonds belong to the class of interactions that are named as the σ-hole and π-hole bonds. The σ-hole bond is an interaction between the σ-hole characterized by the positive electrostatic potential and the electron rich regions such as lone electron pairs, π-electron systems, in other words, centers paying a role of Lewis bases. The σ-holes may be observed for elements of the 14–18 groups of the periodic system and the corresponding interactions with Lewis bases are named; tetrel, pnicogen, chalcogen, halogen and aerogen bonds, respectively. On the other hand, π-holes also characterized by the positive electrostatic potential are observed for centers in planar molecules or planar fragments of molecules in regions above those planes. π-holes may be attributed to triel centers (13th group of the periodic system). The boron and aluminium trihydrides and trihalides are examples of molecules where triels are characterized by π-holes. The mechanism of the triel bond formation is very similar to the mechanism of the formation of the hydrogen bond. It is the Lewis acid – Lewis base interaction where the electron charge transfer from the base unit to the acid one is observed. Next there is outflow of the electron charge from the triel center to the other parts of the Lewis acid unit; in other words the positive charge of the triel center increases as a result of complexation. The triel bonds are often very strong and often they possess characteristics of typical covalent bonds; this is confirmed by the QTAIM (Quantum Theory of Atoms in Molecules) and NBO (Natural Bond Orbital) approaches. For example, for the triel bonds the bond paths between the triel center and the Lewis base center are observed with the bond critical points (BCPs) attributed to those paths. Similarly for the A-H…B hydrogen bonds the H…B bond paths are observed. The parameters of those BCPs often indicate the covalent character of the triel bonds and analogously those characteristics for H-bonds may also indicate the covalent character of the latter interactions. It is very interesting that the triel bonds are observed experimentally in the real systems; for example in crystal structures. The triel center which is trivalent and possesses the trigonal configuration is hypovalent; it means that the octet rule is not obeyed here because of the valence electrons´ deficiency (the triel center possesses six valence electrons in such species). Thus it may interact with one Lewis base ligand reaching rather stable octet and tetrahedral configuration. If the trivalent triel center interacts with two Lewis base ligands thus it may lead to the configuration of the trigonal bipyramid with the hypervalent and pentavalent triel center. These kinds of the triel species occur in crystal structures that are described here.
Źródło:
Wiadomości Chemiczne; 2017, 71, 7-8; 447-471
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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