[molpro-user] Calculation for excited Ne+

[Enrico Bodo]

The following input works, but you cannot do CI unless you use the "noexc" option and substantially use only the reference functions. This is useful if you need to do spin orbit calculations. 


*** Titolo

gprint,basis
gprint,orbital

basis, vdz

geometry={
Ne       0.000000        0.00000        0.00000
}

{rhf;wf,10,1,0; core,0,0,0,0,0,0,0,0; occ,2,1,1,0,1,0,0,0}

{rhf, nitord=1; wf,9,1,1; rotate,1.1,2.1,0; core,0,0,0,0,0,0,0,0; occ,2,1,1,0,1,0,0,0; open, 1.1;}

put,molden,p.molden

{multi;
frozen,0,0,0,0,0,0,0,0;
closed,0,0,0,0,0,0,0,0;
occ,2,1,1,0,1,0,0,0;
freeze,2.1;
restrict,1,1,2.1
wf,9,1,1}

---
 


2013/5/9 Lorenzo Lodi <l.lodi at ucl.ac.uk>
Hello, thank you all for your suggestions. Unfortunately I haven't yet
been able to compute the energy of this core-hole state with MRCI.
I can get the energy with CASSCF by doing something like:

{RHF; WF,nelec=9,symmetry=1,spin=1; ORBPRINT,0}
{CASSCF; OCC, 2,1,1,0,1,0,0,0; CLOSED,0,0,0,0,0,0,0,0;
FROZEN,0,0,0,0,0,0,0,0;
{ITERATIONS;
DONT  , WERNER  , 1, TO, 20;
}
WF,nelec=9,symmetry=1,spin=1; state,1
SELECT
CON, 1,2,2,2,2
}


The first RHF converges to (1s)^2 (2s)^1 (2p)^6; in the following CASSCF
I (I try to) select as only allowed configuration the one where the
lowermost orbitals is singly occupied;
nonetheless, if I allow optimization of the orbitals I get back to the
same configurations as given by the RHF state...
When I try to do MRCI using the CASSCF wavefunction above either I get
error messages or I never get the energy I want.


On 07/05/13 01:57, Terry Frankcombe wrote:
> Why not simply do the RHF for the neutral, then start selecting configs
> for the CI?
>
> Converging the core hole state should certainly be possible.  But it may
> require a largish multi-state CI.  (Speaking off the top of my head
> here.)
>
>
> On Mon, 2013-05-06 at 17:25 +0100, Lorenzo Lodi wrote:
>> I would like to compute the energy (using Hartree-Fock and then
>> configuration interaction) of an excited state of the Ne+ atomic ion
>> with configuration  (1s)^1 (2s)^2 (2p)^6.
>> I tried
>> {UHF; WF,nelec=9,symmetry=1,spin=1; occ,2,1,1,0,1; open, 1.1; ORBPRINT,0}
>>
>> which seems to work, and produces approximately the correct energy
>> (about 31 hartrees above the ground state of Ne+).
>> On the other hand, the same input using RHF
>> {RHF; WF,nelec=9,symmetry=1,spin=1; occ,2,1,1,0,1; open, 1.1; ORBPRINT,0}
>>
>> converges to the ground state, as if the `open, 1.1' command was
>> ignored. However, if I do UHF and then RHF using UHF orbitals as
>> starting guess then RHF also goes to the correct state. Any comments?
>>
>> When I try to use the RHF orbitals for MRCI ( CISD in this case)
>> {MRCI; WF,nelec=9,symmetry=1,spin=1; STATE,1}
>>
>> I get the error message:
>> CI VECTOR FOR STATE 1 DOES NOT OVERLAP SUFFICIENTLY WITH REFERENCE VECTORS
>> It may help to increase NSTATI, e.g., use OPTION,NSTATI=2
>>
>> Setting NSTATI=2 gives the error
>> MORE STATES THAN REFERENCE CONFIGURATIONS:     2    1
>>
>>
>> What can I do to have MRCI to converge on the correct state?
>>
>> Lorenzo
>>
>>
>> _______________________________________________
>> Molpro-user mailing list
>> Molpro-user at molpro.net
>> http://www.molpro.net/mailman/listinfo/molpro-user
>
>


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-- 
Enrico Bodo  -  Assistant Professor in Theoretical Chemistry 
"La Sapienza" University of Rome
Department of Chemistry

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