[molpro-user] Correct Syntax for CCSD Frozen core Orbitals for Ag2

[Kirk Peterson]

Brian,

the default in Molpro for the ECP28MDF pseudopotential used in the cc-pVDZ-PP basis set (and which "should" be the default in all programs using this basis set) is to keep the 5s and 4d electrons in the valence and keep the 4s and 4p electrons in the core.  The PP itself replaces the first 28 electrons, which includes everything through n=3.  I believe this is actually what you are wanting to do with your clusters.

Like the occ and closed directives, the core directive requires to specify the orbitals by their symmetry irreps.  So if I was looking at the isolated atom, which has D2h symmetry as its highest abelian group, then the default core directive would be:

{ccsd(t);core,1,1,1,0,1}

which freezes the 4s and three components of the 4p.  You can always see the default frozen core for your particular molecular symmetry by inspecting the output towards the end of the integral calculation section.  There will be a section that gives the number of orbitals in each irrep for various categories:

NUMBER OF CONTRACTIONS: 
NUMBER OF CORE ORBITALS:
NUMBER OF VALENCE ORBITALS:
 
The one for Core of course is the default frozen core and the sum of "valence" and "core" by the way gives the full valence CAS occupation.

best regards,

-Kirk

On Sep 23, 2012, at 6:18 AM, Brian Napolion <brian_napolion at yahoo.com> wrote:

> 
> Hello,
> I am new to MOLPRO. I see this program drops or freezes the specified core orbitals differently than other programs. What is the correct key word to use if I want to 
>  use a ECP-28 and drop eight of the 3d10 electrons and all of the 4p6 electrons. That would give me the a total of 8e's divided by 2, which means I am dropping 4 molecular orbitals for each silver atom( leaving 5s1 and 4d10 to participate in correlation). I would like to do this for different ag clusters such as ag4.
> 
> 
> Would I use the "core" or "frozen" key words. For instance ag3 would it be
> FROZEN,12 ?
> 
> The default I believe for frozen core orbitals with a ECP-28 in molpro is to drop everything but the 5s1 electron, and the 3d10 -  4p6 - 4d10  are not included
> 
> Below is my input file for ag4, what else would I need to correctly set this up.
> 
> memory,50,m
> include procedures
> basis=cc-pVDZ-PP
> geometry={angstroms;
>                    X;
>                    X,1,XX;
>                    AG,2,RS,1,90;
>                    AG,2,RS,1,90,3,120;
>                    AG,2,RS,1,90,3,-120;
>                    AG,2,RL,1,90,3,180;
>                    }
> RS=1.61853532
> RL=3.11497958
> XX=1.0
> hf
> CCSD(T)
> DUMMY,1,2
> {optg;
> ACTIVE,RS,RL;}
> 
> 
> 
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