Hirshfeld-based atomic population analysis of the B, N doping effect in zigzag graphene nanoribbons: π electron density as requirement to follow the B, N doping guidelines
Résumé
In this work, we present an atomic population study within the Fractional Occupation Hirshfeld-I (FOHI) scheme applied to several pristine, boron-, nitrogen- and B, N-doped non-periodic zigzag graphene nanoribbons (always using a double carbon replacement). To accomplish this task, we have considered the singlet–triplet energy gap as a criterion to check the most reliable electron density. B2PLYPD double-hybrid functional provides the most accurate relative energies in comparison with the other methods, but similar atomic populations are obtained in most cases. Moreover, in spite of the observed different behavior concerning the population of B, N dopants and their corresponding p- and n-type doping effects, the FOHI atomic populations are in excellent agreement with the widely accepted electronegative scale. Nevertheless, we propose to employ a more appropriate electron partitioning strategy taking into account the contribution of π-symmetric orbitals. It provides the expected population results according to doping guidelines. In any case, both kinds of populations describe in a similar way the mesomeric effects and the edge variations after replacing two carbons by either two boron or nitrogen atoms. On the contrary, the populations point out a different behavior when the systems are doped with one boron and one nitrogen simultaneously.