heavy atoms without ecp

[fru14909]

Hello,

how can I avoid the use of ecps for heavy atoms such as Pb?
Whenever I optimize the geometry of my molecule (consisting of Pb and Se) with jobex, the molecule is completely distorted. I removed the ecp, but then eht did not work anymore.
What can I do?

Thanks in advance

[Arnim]

Hi,

it is in general not a good idea to remove ECP and then just use the remaing basis functions. That will get something completely unbalanced. You would have to use an all electron basis set, if you want abstain from using an ECP.

However, ECPs usually work very well. I would think that there might be other obstacles in your system.

Cheers,

Arnim

[fru14909]

Hi,

for more cage-like systems the geometry optimization worked well with ecps. This molecule is built like ammonia, but geometry optimization gives a (unrealistic) planar transition form.
I already tried an all electron basis set, but then the eht guess does not work, although I added $ehtdef and $ehtao paragraphs in the basis file.

Cheers

[Arnim]

Hi,

you can try to find an all electron basis set here:
https://bse.pnl.gov/bse/portal
Download it in Turbomole format and copy it in basis.
Remove the $ecp from control and ecp in $atoms. (In older version remove also $rundimensions)
Then run hcore and start dscf. (For ridft you would have to create an appropriate auxbasis first)

That should do the trick,

Arnim

[Scoops]

Hi,

I'm having an issue with running all electron calculations too (on some small actinide molecules). I have removed the ecp from the control file, but having a problem with using both eht and hcore, with the following message coming up after reading the basis sets, when using hcore:

 symmetry group of the molecule :   c2v

 the group has the following generators :
   c2(z)
   mirror plane sigma(xz)

    4 symmetry operations found

 there are 4 real representations :   a1   a2   b1   b2

 maximum number of shells which are related by symmetry :  2

  missing closed shell occupation number declaration 

****
I haven't tried manually specifying the occupation numbers, would you recommend giving that a go? If so any advice on how to go about it? 

Thanks in advance

Sophie