The passage of alkali metal cations through the pores in phenine and N-doped phenine nanotubes

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Phenine nanotubes , both pristine (PNTs) and N-doped (NPNTs), are a unique novel class of nanotubes with the precise atomic structure and regularly positioned pores on their sidewalls. In this work, we theoretically study the passage of alkali metal cations (M + = Li + , Na + , and K + ) through the PNT (P-pores) and NPNT pores (N-pores). A thorough theoretical analysis of the interaction mechanism between M + and both types of pores has been carried out by the symmetry-adapted perturbation theory . The obtained energy barriers (E b ) for the motion of M + through the pores have been calculated to be 5.7, 23.2, 61.2 kcal/mol (P-pore) and 12.1, 28.4, 71.1 kcal/mol (N-pore) for Li + , Na + , and K + , respectively. It has been established that the small E b values for Li + are due to the very moderate magnitude of the exchange energy term (E ex ). At the same time, exchange interactions affect larger Na + and K + cations much. Dispersion energy (E disp ) magnitudes are non-negligible in only one case of K + . Induction and electrostatic energies are the main parts of attracting interactions. The M + passage through the N-pore is accompanied by the larger E b values owing to the negatively charged regions at the N atoms of the pores. We suppose that results, presented in this theoretical work, shed some light on the nature of the interactions between alkali metal cations and the sidewall pores of new types of nanotubes, and they may also benefit the design of novel applications of such tubes.