vibeqc.mayer_bond_orders

vibeqc.mayer_bond_orders(result, basis, molecule)[source]

Mayer bond-order matrix, shape (n_atoms, n_atoms).

In terms of the spin-summed density P and spin density R:

B_AB = sum_{mu in A, nu in B} [

(P S)_mu,nu (P S)_nu,mu + (R S)_mu,nu (R S)_nu,mu

]

The spin term is zero for RHF/RKS. For UHF/UKS the same definition is evaluated as 2 * [(P_alpha S)^2 + (P_beta S)^2]. This is distinct from a Wiberg index, which squares the density transformed to a Löwdin orthonormal basis.

Off-diagonal entries are atom-pair bond orders; diagonal entries are zero.

Parameters:

  • basis (vibeqc._vibeqc_core.BasisSet)

  • molecule (vibeqc._vibeqc_core.Molecule)

Return type:

ndarray