Multiwfn forum

sourikanair

Member

Registered: 2020-05-27

Posts: 12

NTO analysis error

I did TDDFT calculations using ORCA and loaded .gbw file to run NTO analysis. Did calculation and got value of HOMO-LUMO energy.

But when I repeat the process again I am not getting energy gap. HOMO and LUMO have same energies

55(H ) --> Charge:  1.000000  x,y,z(Bohr): -11.214523  -3.650781   0.598930
   56(H ) --> Charge:  1.000000  x,y,z(Bohr):  -6.178762   1.802666  -4.288639
   57(H ) --> Charge:  1.000000  x,y,z(Bohr):  -0.057032  -5.519588   2.665837
Note: Orbital   105 is HOMO, energy:    0.978720 a.u.   26.632331 eV
       Orbital   106 is LUMO, energy:    0.978720 a.u.   26.632331 eV
       HOMO-LUMO gap:    0.000000 a.u.    0.000000 eV      0.000000 kJ/mol

What may be the reason?

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: NTO analysis error

This is quite reasonable. Because after NTO transformation, the eigenvalue of the orbitals is no longer orbital energy but contribution of NTO to the selected electronic excitation. An occupied and a unoccupied NTO compose a NTO pair; in each NTO pair the two NTOs share the same eigenvalue.

If you are still confused, please check Section 3.21.6 of Multiwfn manual to gain basic knowledges about NTO method.