negative ocupations numbers in a CASPT2 calculation (-1.06)


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Posted by J.J on January 30, 2014 at 11:47:26:

Hi everyone

I made a calculation of the benzene excímer and i obtain negative occupation numbers. The active space was chosen correctly; i understand that it may be result of the accuracy of the numerical methods employed in the calculation, but a occupation number of -1.6, is a big mistake

below I submit my input file
////////////////////////////
&GATEWAY
coord=benzene.xyz
basis=bdzr
Group= XYZ
&SEWARD
&SCF
&RASSCF
symmetry=2;
spin=1;
nactel=12 0 0;
INACtive=18 18;
Ras2=6 6;
ALTEr= 7; 1 17 19; 1 22 27; 1 23 28; 1 24 38; 2 22 28; 2 23 29; 2 24 39
LumOrb
&CASPT2
DENSity
natural
////////////////////////////

////////////////////////////
24
angstrom
C 0.699767 1.212032 1.800000
C 1.399534 0.000000 1.800000
C 0.699767 -1.212032 1.800000
C -0.699767 -1.212032 1.800000
C -1.399534 0.000000 1.800000
C -0.699767 1.212032 1.800000
C 1.399534 1.800000 -1.800000
C 0.699767 0.587968 -1.800000
C -0.699767 0.587968 -1.800000
C -1.399534 1.800000 -1.800000
C -0.699767 3.012032 -1.800000
C 0.699767 3.012032 -1.800000
H -1.240080 3.947882 -1.800000
H -2.480160 1.800000 -1.800000
H -1.240080 -0.347882 -1.800000
H 1.240080 -0.347882 -1.800000
H 2.480160 1.800000 -1.800000
H 1.240080 3.947882 -1.800000
H -1.240080 2.147882 1.800000
H -2.480160 0.000000 1.800000
H -1.240080 -2.147882 1.800000
H 1.240080 -2.147882 1.800000
H 2.480160 0.000000 1.800000
H 1.240080 2.147882 1.800000
///////////////////////////
where bdzr is the Roos Augmented Double Zeta basis set, obtained of the website: https://bse.pnl.gov/bse/portal. I also understand that can be used a C2h symmetry group, but the point is find the source of the error and not the calculation itself.

so my question is, i´m doing something wrong?

thanks in advance!


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