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Abstract
Nanomaterials based on carbon nanotubes (CNT) and graphenes attract a lot of attention of researchers as the materials capable to raise the development of various industries to the new level, and first of all, of the chemical and electronic sectors. In addition to known experimental methods, new nanosystems are widely studied using advanced tools of quantum-chemical approaches. Modern theoretical methods are of great interest due to their ability to interpret known experimental facts and predict properties of non-synthesized compounds yet. This paper reviews results of theoretical studies performed using the density functional theory (DFT) methods to obtain data on the structure and electronic properties of single-walled CNT and graphene, modified with various impurities, with covalent-ionic and non-covalent binding mechanisms. New computational methods are briefly described that are currently employed to treat the dispersion interaction and enhance possibilities of DFT tools in systems where the van der Waals forces play a significant role. Particular attention is paid to the characteristics of carbon nanomaterials containing technologically important hydroxyl, carboxyl and amino groups. It is shown that the specific peculiarity of band structures of discussed in the literature CNT functionalized by OH, COOH, NHn and CONH2 groups is the partially occupied band in the neighborhood of the Fermi level, which directly affects the CNT conductivity. Modification of graphene layers is analyzed that interact with hydrogen, fluorine, bases of nucleic acids and the metal substrate surface. We also provide accuracy estimates for the calculations of interatomic bond lengths, interaction energy and band gap carried out in the literature using a variety of DFT approximations.
Highlights
Experimental study of the properties of individual carbon nanotubes (CNT) and graphene layers of atomic thickness is still the challenge due to high requirements to the equipment and time-consuming manipulation of nanoscale objects
We briefly describe the main computational methods currently used to treat the dispersion interaction when modeling the adsorption on the surface of the CNT and graphene
The basic requirement for any calculation scheme based on density functional theory (DFT) is the provision of asymptotic behavior of interaction energy according to the law –1/r6 for the particle interaction in the gas phase, where r is a distance between particles
Summary
Experimental study of the properties of individual carbon nanotubes (CNT) and graphene layers of atomic thickness is still the challenge due to high requirements to the equipment and time-consuming manipulation of nanoscale objects. Theoretical modeling allows the tracing of the “structure – property” relations at full control of the composition and structure of test objects which is often impossible for experimental methods Such studies are important when characterizing functionalized CNT and graphenes, and the most important is the level of accuracy to be suggested by the particular approach. The most promising are methods that do not rely on external inputs, but determine the dispersion interaction energy directly as the electron density function This is primarily the more general strategy, and such methods are on the third level of the hierarchy [3]. The basis of these methods is the use of recently developed long-range non-local correlation functionals as the additional term in the expression for total exchangecorrelation energy
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