What is "Occ", "E", " r^2","Bnf" and "Vector" ?

  • Guest -
After QM\MM calculation, I get some information, but I don't know how to analyse. I don't know what is "Occ", "E", " r^2","Bnf" and "Vector "

                      DFT Final Molecular Orbital Analysis

Vector   36  Occ=2.000000D+00  E=-1.003594D+01
MO Center= 4.0D+01, 3.2D+01, 1.9D+01, r^2= 2.8D-02
Bfn. Coefficient Atom+Function Bfn. Coefficient Atom+Function
----- ------------ --------------- ----- ------------ ---------------
262 0.563637 20 C s 263 0.459316 20 C s

Vector   37  Occ=2.000000D+00  E=-1.175142D+00
MO Center= 4.0D+01, 2.9D+01, 2.4D+01, r^2= 8.3D-01
Bfn. Coefficient Atom+Function Bfn. Coefficient Atom+Function
----- ------------ --------------- ----- ------------ ---------------
500 0.414547 35 N s 508 0.353656 35 N s
546 0.272788 37 O s 523 0.267435 36 O s
504 0.221614 35 N s 554 -0.187149 37 O s
550 0.179655 37 O s 527 0.179511 36 O s
531 -0.164303 36 O s

  • Guest -
Explanation of terms in the orbital output
The information you are considering is very common and used in almost all quantum chemistry calculations. You are looking at the molecular orbitals which for the modules you are using are expressed in terms of Gaussian basis functions. The terms you asked about are:
  • vector - A single molecular orbital expressed as a linear combination of Gaussian atomic orbitals (LCAO), also referred to as basis functions
  • Bfn - Refers to the contribution of a particular basis function to a given vector. The number under Bfn is the position of the basis function in the overall basis set, the coefficient is the weight of that basis function, next is the number of the atom in your geometry followed by its chemical symbol and the angular momentum of the basis function.
  • Occ - The occupation number of the particular molecular orbital.
  • E - The orbital energy, i.e. the eigenvalue of the Fock or Kohn-Sham matrix corresponding to the particular molecular orbital.
  • r^2 - A measure for how diffuse a molecular orbital is.
I hope this information proves useful.

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