Gbasis

gbasis stores information about the Gaussian basis functions that were used in the calculation. The information is stored per atom using the same conventions as PyQuante. Specifically, gbasis is a list (per atom) of lists (per Gaussian basis function) of tuples of length 2 consisting of orbital type (e.g. 'S', 'P' or 'D') and a list (per contracted GTO) of tuples of size 2 consisting of the exponent and coefficient. Confused? Well, here's gbasis for a molecule consisting of a single C atom with a STO-3G basis:

[ # per atom [   ('S',[        (71.616837, 0.154329),        (13.045096, 0.535328),        (3.530512, 0.444635),        ]), ('S',[       (2.941249, -0.099967),        (0.683483, 0.399513),        (0.222290, 0.700115),        ]), ('P',[       (2.941249, 0.155916),        (0.683483, 0.607684),        (0.222290, 0.391957),        ]), ]   ]

Development notes
It also needs to be noted whether any D and F functions are pure (5D, 7F) or Cartesian (6D, 10F). PyQuante can only handle Cartesian functions, but we should extract this information in any case. We will need to extend the PyQuante basis set format to include this.