[molpro-user] Calculation for excited Ne+

[Lorenzo Lodi]

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
>>
>>
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>
>