Table 2 lists the evaluated VS(r) parameters for the pristine and
different models of N-doped BC3NTs. Fig. 3 also indicates the
overall patterns of surface electrostatic potential maps for the
tubes. In the case of the pristine tube, the electron-donating
hydrogens cause the outer carbon surfaces to become negative,
with VS,min of about 8 kcal/mol. The inside of the tube is