Example: consider a T=4 virus (= 4 x 60 subunits = 240 subunits)

The minimum free energy solution is to divide each triangle into 4 further triangles and place a subunit at each corner. There will be 12 x 20 subunits, i.e. 240 with 12 pentamers and 30 hexamers. They are obviously not equivalent, but 180 are and the remaining 60 are making similar contacts. They are said to be quasi equivalent. Protein subunits are not spaced independently but cluster because this maximizes the intermolecular interactions which stabilize the particle. One consequence of this clustering is that bonds between subunits in a capsomer are stronger than bonds between capsomers.