An application of the CNDO/2 and INDO theories to the calculation of molecular quadrupole moments

Values of molecular quadrupole moments are calculated using the CNDO/2 and INDO methods and compared with experiment and other calculations. The agreement is good, except for π systems both linear and planar. Consideration of this disagreement suggests that use of π AO's which are less compressed perpendicular to the molecular plane or the internuclear axis may produce better results. A preliminary method of this type is adopted to obtain satisfactory theoretical results for π systems, too.