[molpro-user] Lattice point of charges

[Ricardo Mata]

Dear Muammar,

In your second calculation, where you place your point charge at 1 Bohr (let's call this P1) and turn your hydrogen atom (let's call this P2) into a ghost, the basis functions are centered on P2. So, although the electron naturally stays at P1, the basis functions are insufficient to describe the electron orbital space. When you place the lattice charge close to your original atom, then the description improves (since now the electron is staying next to your charge and the functions are also located there). This is what should be expected.

Best wishes,
Ricardo

On Oct 1, 2012, at 3:04 PM, Muammar El Khatib wrote:

> Dear Molpro users,
> 
> I'm trying to use the lattice point of charges in MOLPRO, and a doubt has
> raised. Maybe it is a mistake of mine, and I hope somebody could shed some
> light on this.
> 
> For example, if I run the hydrogen atom using as input file the one I show
> below:
> 
> --------------8<-----------------------8<---------------------------8<--------
>    ***, H
>    gprint,basis;
>    gprint,orbital;
>    gprint,civector;
>    mass,print
>    symmetry,x,y,z;
> 
>    geometry=
>    {
>     H    0,    0.0,       0.0,     0.0;
>     }
> 
>    basis=6-31g**
> 
>    int;
> 
>    {hf;
>    occ,1,0,0,0,0,0,0,0;
>    wf,1,1,1;
>    }
>    put,molden,hhf.molden
>    ---
> 
> --------------8<-----------------------8<---------------------------8<--------
> 
> I obtain an energy that is -0.49823291. But now, If I set the hydrogen atom as
> dummy¹ (so that its charge become 0), and then I place a point of charge of "1"
> at 1 bohr (0.529177249Å)[that is the most probable distance between proton and
> electron in the hydrogen's ground state] I obtain an energy that is -0.33978462
> (see input, and lattice file below).
> 
> --------------8<-----------------------8<---------------------------8<--------
>    ***, H
>    gprint,basis;
>    gprint,orbital;
>    gprint,civector;
>    mass,print
>    symmetry,x,y,z;
> 
>    geometry=
>    {
>     H    0,    0.0,       0.0,     0.0;
>     }
> 
>    basis=6-31g**
> 
>    int;
>    dummy,H;    ! I placed here so that it is not reseted by the int card.
>    LATTICE,INFILE=hlattice
>    {hf;
>    occ,1,0,0,0,0,0,0,0;
>    wf,1,1,1;
>    }
>    put,molden,hhf.molden
> 
>    ---
> 
> lattice file:
> 
> Point Charges
> 1
> 0.0,0.0,0.529177249,1.00,0
> 
> --------------8<-----------------------8<---------------------------8<--------
> 
> Why is this difference in the energy? After doing some tests, for "reproducing"
> the energy obtained without point of charges, I found that the lattice file
> should be approximately:
> 
> Point Charges
> 1
> 0.0,0.0,0.0301091,1.00,0
> 
> And thus, I obtained an energy value that is -0.49624441.
> 
> Regards,
> 
> 1. http://www.molpro.net/info/current/doc/manual/node107.html
> 
> PS. I have searched a lot in the mailing list archives, and there is no much
> information about it.
> --
> Muammar El Khatib.
> Linux user: 403107.
> Key fingerprint = 90B8 BFC4 4A75 B881 39A3 1440 30EB 403B 1270 29F1
> http://muammar.me | http://proyectociencia.org
>  ,''`.
> : :' :
> `. `'
>   `-
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