Физико-химические аспекты изучения кластеров, наноструктур и наноматериалов (Dec 2024)
Description of complexation thermodynamic parameters for alkanes and polyaromatic hydrocarbons in the framework of semiempirical methods
Abstract
The paper presents a comparative analysis of quantum chemical semiempirical methods for calculation of the binding thermodynamic parameters for CnH2n+2 alkanes (n=6–14) and polyaromatic hydrocarbons of the coronene series as model structures of the graphene surface. Two types of orientation of alkane molecules are considered depending on the relative position of the C–C–C «zigzag» plane of alkanes within the polyaromatic hydrocarbons plane: parallel and perpendicular. The parallel arrangement of alkane molecules on the polyaromatic hydrocarbon surface is revealed to be more energetically advantageous than the perpendicular one. The enthalpy, entropy, and Gibbs energy of alkane formation and binding to polyaromatic hydrocarbons are calculated using the PM3, RM1, PM6-DH2, PM6-D3H4, and PM7 methods. It is shown that the first two methods are improper for describing the intermolecular C–H/π interactions in alkane – polyaromatic hydrocarbon systems, since the Gibbs binding energy estimated in them has positive values, which is inconsistent with the available literature data. The use of the PM6 method with DH2 correction for dispersion interactions and hydrogen bonds is optimal. The values of binding enthalpy in alkane – tricircumcoronene complexes calculated using PM6-DH2 and RM6-D3H4 methods are in good agreement with experimental data on the enthalpy of adsorption of alkanes on the graphite/graphene surface, as well as data from molecular dynamic modeling. However, according to the Gibbs binding energy in the considered alkane complexes with parallel and perpendicular orientation of alkanes on tricircumcoronene, only the PM6-DH2 method gives values that correspond in the best way to the available data on the energy preference of such complexes.
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