While the concept of non-additivity has been studied for atom clusters

While the concept of non-additivity has been studied for atom clusters, insulators, and SWCNTs, it seems to be overlooked for BNNTs. The methods used were essentially the same as in our previous work 67-70. We define the interaction energy E(i)(BNNT-Ni-4H_2) among three subsystems, the BNNT (N40B40), the metal (Ni), and the (4H2) molecules as
E(i)(BNNT-Ni-4H_2 )=E(BNNT-Ni-4H_2 )-E(BNNT)-E(Ni)-E(4H_2 ), (4)
This energy can be decomposed into three pairwise components and a non-additive term? ??^((nadd) ); and no geometrical relaxation is allowed within a subsystem
In Table 4 we present total interaction energies of 4H2-Ni-BNNT-?=0, 15, 30, 45 complexes, pairwise additive components, and the non-pairwise additive term. In Table (4), the total interaction energies of E_((i) ) (BNNT-Ni-4H_2 ) complexes are seen to be dominated by the pairwise additive component? E?_((i) ) (BNNT-Ni). An important issue in any study of a support–metal system is the extent to which the support (BNNT) influences the interaction of an adsorbate (4H2) with the metal (Ni). TheE_((i) ) (BNNT-Ni)term is always greater than theE_((i) ) (Ni-4H_2 ) term. This implies that the binding of 4H2 is mostly dominated by the support–metal contributionE_((i) ) (BNNT-Ni), followed by the pairwise metal–dihydrogen additive contributionE_((i) ) (Ni-4H_2 ). We may, therefore, conclude that the BNNT support has a considerable effect on the interaction of 4H2 with Ni, and its role is not restricted to supporting the metal. In other words, the adsorption energy of 4H2 depends on the bending effects and the amount of charge transfer from the metal Ni which in turn depends on the electronegativity of the BNNT support. The complex 4H2-Ni-BNNT-?=15, 30, 45 are characterized by larger pairwise terms relative to those of the complex 4H2-Ni-BNNT-?=0.