Energetics

Table 1: Average binding energy per electron for carbon and boron nitride systems. The energies of the graphitic phases are for isolated sheets.

C systems			BN systems
Benzene	2.24	1.99	Borazine
PPV	2.22	1.98	PVB
PPP	2.22	1.98	PBZ
Graphite	2.20	1.96	Graphitic BN

To investigate the energetics of these different structures, we have calculated their total binding energies with respect to their constituent atoms. Trends in the energetics can be observed in both the average bond energies (i.e. the total binding energy divided by the number of bonds in the structure) [27] and the binding energy per electron (i.e. the total binding energy divided by the number of valence electrons), which we report in Table 1. We compare the energies of the (one-dimensional) polymers to the (zero-dimensional) molecules (benzene and borazine) used to build them, and to the corresponding (two-dimensional) graphitic forms. As expected, the polymers fall energetically in between these two extremes, with the same trend for the boron nitride and the carbon compounds, and small energy variations within compounds of the same family. This suggests that the chemistry of the BN polymers should be similar to that of the carbon polymers.