In each case, the dimer bond length is increased somewhat compared to the clean dimer bond length is increased somewhat compared to the clean dimer (2.37 Ã… ).
The SiH 2 groups diffuse around the surface (2) until two of them react to form a monohydride dimer (3 ).
The four atoms which make up the distorted square are shown by filled circles, the substrate dimer atoms are shown by open circles.
Nevertheless the PSII core region is clearly 2-fold symmetric and closely resembles the averaged PSII core dimer top view.
Differences between the dimer and trimer profiles revealed sequence patterns that match and extend experimental studies of oligomer specification.