The normal density matrix is composed of atomic orbitals, that is s,
px, py and pz. PI allows the user to see how each atom-atom interaction
is split into σ, π,
and Δ
bonds. The
resulting "density matrix" is
composed of the following basis-functions: s-σ,
p-σ, p-π, d-σ,
d-π, d-δ.
The on-diagonal terms give the hybridization
state, so that an sp2 hybridized system would be represented as
s-σ:
1.0, p-σ:
2.0, p-π:
1.0.