Mr. Acero,

Could you upload your roiute section and the output data, showing a charge 0.5? In addition, what are the initial charge and multiplicity of your system?

Please upload the related files.

Yup, this is pretty much not possible, so please upload the output file (or at least the part with NBO charges).

this is one the files. I still don understand why

The total charge of your system is '0' as it is shown in your output data:

.................

Summary of Natural Population Analysis:

Natural Population

Natural -----------------------------------------------

Atom No Charge Core Valence Rydberg Total

-----------------------------------------------------------------------

C 1 -0.20908 1.99911 4.19331 0.01667 6.20908

C 2 -0.21759 1.99903 4.20035 0.01821 6.21759

C 3 -0.10247 1.99878 4.08382 0.01987 6.10247

C 4 -0.10247 1.99878 4.08382 0.01987 6.10247

C 5 -0.21759 1.99903 4.20035 0.01821 6.21759

C 6 -0.20909 1.99911 4.19331 0.01667 6.20909

C 7 -0.37317 1.99889 4.34954 0.02473 6.37317

C 8 -0.37318 1.99889 4.34955 0.02473 6.37318

C 9 -0.10247 1.99878 4.08382 0.01987 6.10247

C 10 -0.10247 1.99878 4.08382 0.01987 6.10247

C 11 -0.21759 1.99903 4.20035 0.01821 6.21759

H 12 0.19458 0.00000 0.80327 0.00215 0.80542

C 13 -0.20909 1.99911 4.19331 0.01667 6.20909

C 14 -0.20908 1.99911 4.19331 0.01667 6.20908

C 15 -0.21759 1.99903 4.20035 0.01821 6.21759

H 16 0.20860 0.00000 0.78914 0.00226 0.79140

H 17 0.19561 0.00000 0.80264 0.00175 0.80439

H 18 0.19458 0.00000 0.80327 0.00215 0.80542

H 19 0.19458 0.00000 0.80327 0.00215 0.80542

H 20 0.19561 0.00000 0.80264 0.00175 0.80439

H 21 0.20860 0.00000 0.78914 0.00226 0.79140

H 22 0.19561 0.00000 0.80264 0.00175 0.80439

H 23 0.19561 0.00000 0.80264 0.00175 0.80439

H 24 0.19458 0.00000 0.80327 0.00215 0.80542

Li 25 0.88496 1.99801 0.10747 0.00956 2.11504

=======================================================================

* Total * 0.00000 29.98346 66.71838 0.29816 97.00000

..................

So, how you have obtained the discussed value '0.5', when there is shown a quantity '0'?

I have requested the pop=nbo inside an opt calculations, one of the SCF steps gives Zero as you mention, but please take a look in the last step of the calculations you will find

  Natural Population

Natural -----------------------------------------------

Atom No Charge Core Valence Rydberg Total

-----------------------------------------------------------------------

C 1 -0.08041 0.99955 2.07283 0.00803 3.08041

C 2 -0.06918 0.99951 2.06092 0.00875 3.06918

C 3 -0.05629 0.99939 2.04719 0.00970 3.05629

C 4 -0.05629 0.99939 2.04719 0.00970 3.05629

C 5 -0.06918 0.99951 2.06092 0.00875 3.06918

C 6 -0.08041 0.99955 2.07283 0.00803 3.08041

C 7 -0.04662 0.99944 2.03659 0.01058 3.04662

C 8 -0.04662 0.99944 2.03660 0.01058 3.04662

C 9 -0.05629 0.99939 2.04719 0.00970 3.05629

C 10 -0.05629 0.99939 2.04719 0.00970 3.05629

C 11 -0.06918 0.99951 2.06092 0.00875 3.06918

H 12 0.09601 0.00000 0.40291 0.00109 0.40399

C 13 -0.08041 0.99955 2.07283 0.00803 3.08041

C 14 -0.08041 0.99955 2.07283 0.00803 3.08041

C 15 -0.06918 0.99951 2.06092 0.00875 3.06918

H 16 0.10029 0.00000 0.39860 0.00111 0.39971

H 17 0.09694 0.00000 0.40219 0.00088 0.40306

H 18 0.09601 0.00000 0.40291 0.00109 0.40399

H 19 0.09601 0.00000 0.40291 0.00109 0.40399

H 20 0.09693 0.00000 0.40219 0.00088 0.40307

H 21 0.10029 0.00000 0.39860 0.00111 0.39971

H 22 0.09694 0.00000 0.40219 0.00088 0.40306

H 23 0.09693 0.00000 0.40219 0.00088 0.40307

H 24 0.09601 0.00000 0.40291 0.00109 0.40399

Li 25 0.44442 0.99885 0.05223 0.00450 1.05558

=======================================================================

* Total * 0.50000 14.99157 32.86676 0.14167 48.00000

Mr. Acero,

First, NBO computations are within the framework of one cycle. So that, there is not optimization steps in your file.

The table which I have shown is the 'Summary'-table, because of NBO alpha and beta spin densities are separately computed (for open shell systems) using the following equation:

NBO(alpha)x = q(nuc charge)x/2 - q(alpha)x.

The same equation is valid to the beta spin densities.

And as you can see the second table in the output is assocuated with the alpha-spins.

Additional link: http://gaussian.com/population/

Dear Ms Bojidarka,

A really appreciate your answer and explanation, now it is clear for me.

Thank you very much!