[molpro-user] Huge Davidson cluster corrections

[Zork Zou]

Hi,

In the following test job, the lowest 3 quartet states of Pt+ ion are calculated by SA-CASSCF and then MRCI using the 2010.1 version of the program. It's found that some of the Davidson cluster corrections with fixed reference are huge, nevertheless they are seldom used, but the old version of correction looks fine. For example,

 RESULTS FOR STATE 1.4
 =====================

 Maximum overlap with reference state  2

 Coefficient of reference function:   C(0) = 0.96156132 (fixed)   0.96156133 (relaxed)   0.96156133 (rotated)

 Energy contributions of configuration classes

 CLASS          SQ.NORM        ECORR1        ECORR2
 +++++++++++++++++++++++++++++++++++++++++++++++++++
 Internals**************    0.00000000   -0.44063954
 Singles  **************   -0.08561890   -0.00658060
 Pairs    **************   -0.39094536   -0.02934927
 Total    **************   -0.47656426   -0.47656941
 +++++++++++++++++++++++++++++++++++++++++++++++++++


 Reference energy                    -118.21513715
 Nuclear energy                         0.00000000
 Kinetic energy                        40.16272361
 One electron energy                 -201.49319220
 Two electron energy                   82.80148564
 Virial quotient                       -2.95527036
 Correlation energy                    -0.47656941
 !MRCI STATE 1.4 Energy              -118.691706560518

 !MRCI STATE 1.4 Dipole moment          0.00000000     0.00000000     0.00000000
 Dipole moment /Debye                   0.00000000     0.00000000     0.00000000

 Cluster corrected energies        *************** (Davidson, fixed reference)
 Cluster corrected energies          -118.73057011 (Davidson, relaxed reference)
 Cluster corrected energies          -118.73057011 (Davidson, rotated reference)

 Cluster corrected energies          -118.21513715 (Pople, fixed reference)
 Cluster corrected energies          -118.72704614 (Pople, relaxed reference)
 Cluster corrected energies          -118.72824991 (Pople, rotated reference)

Input:

***,test
memory,4000,m

basis=vtz-pp

geometry={
Pt
}

{hf;occ,4,1,1,1,1,1,1,0;wf,20,1,0;}

! Pt+: 4F, 4P, 4F
{multi;natorb,ci;
frozen,0;closed,1,1,1,0,1,0,0,0;occ,4,1,1,1,1,1,1,0;
wf,17,1,3;state,2;
wf,17,4,3;state,5;
wf,17,6,3;state,5;
wf,17,7,3;state,5;
}

{ci;
core,0;closed,1,1,1,0,1,0,0,0;occ,4,1,1,1,1,1,1,0;
wf,17,4,3;state,5;
}

{ci,SWAP,ROTREF=-1;
core,0;closed,1,1,1,0,1,0,0,0;occ,4,1,1,1,1,1,1,0;
wf,17,4,3;state,5;
}
---

Best,
Wenli
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