Equidensity surface

One may use different types of molecular cavities and surfaces definitions (e.g. equipotential surfaces, equidensity surfaces, van der Waals surfaces). Among them there is a subset that shares a common trait they consider that a molecule may be represented as a set of rigid interlocking spheres. There are three such surfaces a)... 

The 0-0 axis is practically collinear to the C-H bond for the closed shell state and perpendicular for the open shell one. Also, the 0-0 distance is much larger for the latter than for the former. The C-H bond for the open shell state is long and hence weakened. The spin equidensity surface at 0.02 e /bohr is evocative of the incipient formation of a 1 electron second C3-O2 bond and of a 1 electron bond between Ci and Oi. 

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