HOMO-LUMO gap and energy
Just Got Here
1:08:20 AM PDT - Tue, May 20th 2014
I have done a PBE DFT total energy calculation on trans-azobenzene using 6-31G basis set. The output HOMO LUMO energy are
 HOMO         =      -0.232737
 LUMO         =      -0.095934



 Vector   47  Occ=2.000000D+00  E=-2.042511D-01  Symmetry=au
              MO Center=  8.6D-16, -2.0D-15, -2.6D-17, r^2= 1.1D+01
   Bfn.  Coefficient  Atom+Function         Bfn.  Coefficient  Atom+Function
  ----- ------------  ---------------      ----- ------------  ---------------
    41     -0.231762   5 C  pz              114     -0.231762  17 C  pz
    14      0.215979   2 C  pz               87      0.215979  14 C  pz
     5     -0.193556   1 N  pz               78     -0.193556  13 N  pz
    45     -0.173935   5 C  pz              118     -0.173935  17 C  pz
    59      0.164878   7 C  pz              132      0.164878  19 C  pz

 Vector   48  Occ=2.000000D+00  E=-1.730196D-01  Symmetry=ag
              MO Center=  4.2D-16,  6.9D-16, -2.3D-18, r^2= 2.2D+00
   Bfn.  Coefficient  Atom+Function         Bfn.  Coefficient  Atom+Function
  ----- ------------  ---------------      ----- ------------  ---------------
     3      0.406492   1 N  px               76     -0.406492  13 N  px
     7      0.267589   1 N  px               80     -0.267589  13 N  px
     6      0.243693   1 N  s                79      0.243693  13 N  s
    15     -0.234813   2 C  s                88     -0.234813  14 C  s
    61      0.231512   7 C  px              134     -0.231512  19 C  px

 Vector   49  Occ=0.000000D+00  E=-1.098084D-01  Symmetry=bg
              MO Center= -1.9D-15,  7.1D-15,  1.4D-16, r^2= 7.3D+00
   Bfn.  Coefficient  Atom+Function         Bfn.  Coefficient  Atom+Function
  ----- ------------  ---------------      ----- ------------  ---------------
     5      0.364349   1 N  pz               78     -0.364349  13 N  pz
     9      0.316606   1 N  pz               82     -0.316606  13 N  pz
    41      0.189257   5 C  pz              114     -0.189257  17 C  pz
    45      0.187283   5 C  pz               63     -0.187746   7 C  pz
   118     -0.187283  17 C  pz              136      0.187746  19 C  pz

Vector   50  Occ=0.000000D+00  E=-3.444670D-02  Symmetry=bg
              MO Center= -2.1D-15,  3.1D-15,  2.7D-16, r^2= 1.3D+01
   Bfn.  Coefficient  Atom+Function         Bfn.  Coefficient  Atom+Function
  ----- ------------  ---------------      ----- ------------  ---------------
    27      0.321091   3 C  pz              100     -0.321091  15 C  pz
    54      0.316982   6 C  pz              127     -0.316982  18 C  pz
    36     -0.255164   4 C  pz               50      0.255902   6 C  pz
   109      0.255164  16 C  pz              123     -0.255902  18 C  pz
    23      0.253006   3 C  pz               96     -0.253006  15 C  pz



However, when I looked at each MO, the energies do not match the HOMO-LUMO energy reported earlier. May I ask what is the true HOMO LUMO gap and energy?

Forum Vet
9:27:07 AM PDT - Tue, May 20th 2014
Starting guess
Liuyun
The HOMO and LUMO values that you report at the beginning of your post are relative to the initial guess before the SCF has reached convergence.
Therefore, the HOMO and LUMO values of your run has be extracted from the eigenvalue analysis printed at the end of the run,
i.e. -1.730196D-01 and -1.098084D-01

Just Got Here
9:37:16 AM PDT - Tue, May 20th 2014
Quote:Edoapra May 20th 9:27 am
Liuyun
The HOMO and LUMO values that you report at the beginning of your post are relative to the initial guess before the SCF has reached convergence.
Therefore, the HOMO and LUMO values of your run has be extracted from the eigenvalue analysis printed at the end of the run,
i.e. -1.730196D-01 and -1.098084D-01



Thank you very much! You have cleared my doubt.


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