Bond orders

["Hongbin Du" <hdu -AatT- ned1.sims.nrc.ca>]

Dear CCLers,
 Using Gaussian, NBO, AIMPAC etc., one can obtain several kinds of bond
 orders: AIM bond order, Wiberg Bond order, overlap-weighted NAO bond order,
 NLMO/NPA bond order (bo). Here are the questions:
 (1) Which is 'the best' to describe the bonding in molecules? In our recent
 study, only AIM bond order had the 'right' number (i.e. b.o. ~ 1.4 by
 comparison of the electron densities at the bond critical points with the
 standard compounds, Classical Lewis acid-base theory yields a bo of 1.5,
 while NBO analyses gave various bo around 1.0). Could somebody recommend any
 reference for their comparison?
 (2) What is the physical meaning for the negative NBO bond orders in the ?
 For example:
     Atom-Atom Net Linear NLMO/NPA Bond Orders:
       Atom    1       2       3       ...
       ---- ------  ------  ------  ...
     1.  C  0.0000  0.8174  0.7960  ...
     2.  N  0.8174  0.0000 -0.0104 ...
     3.  H  0.7960 -0.0104  0.0000 ...
      ...
 Thank you,
 Hongbin