VBPT2 calculations

[Slavko Radenkovic]

Dear Fuming,

We are trying to calculate the bond dissociation energy (BDE) for CuF.
Using VBSCF, we obtained BDE= 255.32 kJ/mol (experimental value is 
414 kJ/mol).

When we try VBPT2 using the same structures as in VBSCF, and using 
the VBSCF orbitals as a guess, we got BDE=664.24kJ/mol. This is too 
far from the experimental value.  

We are wondering is there any errors in our VBPT2 calculations?

Please find attached the needed xmvb files for F, Cu and CuF.

Best regards,

Slavko

P.S.

It seems that these files are too big to be attached, so please find them here:

https://www.dropbox.com/s/672bc9brpbrt7pt/CuF.tar.gz?dl=0

https://www.dropbox.com/s/c2vsxfusimww3a5/Cu.tar.gz?dl=0

https://www.dropbox.com/s/mr071bsihvp3xtl/F.tar.gz?dl=0

[应富鸣]

Dear Slavko,

We have noticed your problem and will test your calculaitons.

Best regards,

在 2018年4月20日星期五 UTC+8下午5:50:30，Slavko Radenkovic写道：

[应富鸣]

Dear Slavko,

Sorry for the delay.

I just tested your calculations and I think the reason maybe that your calculation of Cu atom is wrong.

According to your comments, the last 3 orbitals should be dx2-y2 (inactive) dz2(inactive) and 4s(active).

But actually, the main part of these orbitals share the same d part: dxx, dyy, dzz (and s).

So the 3 orbitals may be mixed since Cu atom is sphere.

In your calculation, if you check the VBSCF orbitals carefully, the last 3 converge VBSCF orbitals are dx2-y2, a mixing of dx2-y2 and s, and something like d0 but on the x axis. The orbitals are not what you want, especially for the active part. And this should be the reason.

Attached is my VBSCF calculation with a special initial guess which provides right ordering and shape of the orbitals.

This reduce the energy of VBSCF AND VBPT2 of Cu. So I get the following BDEs:

VBSCF:  224.5 kJ/mol

VBPT2:  388.5 kJ/mol

I think this result should accord with the experiments well.

You may take the VBSCF orbitals from my calculation as initial guess and run VBPT2.

Best regards,

在 2018年4月20日星期五 UTC+8下午5:50:30，Slavko Radenkovic写道：

Dear Fuming,