RAS-2SF calculations for different states

Questions
#1

When I performed RAS-2SF excited state calculations on the DDMX molecule (an example in the Q-chem program), the following problem occurred: After I fixed the same self-consistent field data, the output results completely changed just by changing the number of roots, and they were all different from the data in the ras-2sf reference.
Here are my output files.I only show the first three excited states. The data presented at such low energy levels are completely different.
Can you check my input file and give me some advice for solving this problem?

$comment
  RAS(4,4)-2SF-CI low-lying states of DDMX tetraradical
$end

$molecule
0 5
C           0.000000    0.000000    1.092150
C          -1.222482    0.000000    0.303960
C          -2.390248    0.000000    1.015958
H          -2.344570    0.000000    2.095067
H          -3.363161    0.000000    0.537932
C          -1.215393    0.000000   -1.155471
H          -2.150471    0.000000   -1.702536
C           0.000000    0.000000   -1.769131
C           1.215393    0.000000   -1.155471
H           2.150471    0.000000   -1.702536
C           1.222482    0.000000    0.303960
C           2.390248    0.000000    1.015958
H           2.344570    0.000000    2.095067
H           3.363161    0.000000    0.537932
$end

$rem
  jobtype           sp
  method            rasci
  basis             6-31g*
  max_scf_cycles    200
  scf_convergence 8
  !scf_algorithm     dm
  unrestricted      false         ! RASCI only works with unrestricted orbitals
scf_guess read
sym_ignore true
!RASCI
  RAS_ROOTS         9            ! Compute 9 states
  RAS_ELEC          4             ! Active electrons    (RAS2)
  RAS_ACT           4             ! Active orbitals     (RAS2)
  RAS_OCC           25            ! Doubly occ orbitals (RAS1)
  RAS_DO_HOLE       true          ! Compute hole contributions (RAS1 -> RAS2)
  RAS_DO_PART       true          ! Compute part contributions (RAS2 -> RAS3)
  RAS_SPIN_MULT     0             ! Compute any spin multiplicity
  RAS_NATORB        true          ! Compute natural orbital occupancies
! RAS_ACT_ORB       [26,27,28,29] ! Pick active orbitals
! RAS_NATORB_STATE  2             ! Save natural orbitals of state 2 in file 53.0
! RAS_GUESS_CS      1             ! Force (at least) 1 close shell guess
$end
SCF converges when RMS gradient is below 1.0e-08
 ---------------------------------------
  Cycle       Energy        RMS Gradient
 ---------------------------------------
    1    -306.1969607828      5.54e-09  Convergence criterion met
The disked orbital energies are calculated using alpha and beta Focks
 ---------------------------------------
 SCF time:   CPU 3.67s  wall 0.00s 
<S^2> =          6.000000000
 SCF   energy in the final basis set =     -306.1969607828
 Total energy in the final basis set =     -306.1969607828

 Q-Chem warning in module /public/home/huangxk/qchem/libsym/oriorb.F, line  198:

 OriOrb: Failure to resolve orbital degeneracies.


 Q-Chem warning in module /public/home/huangxk/qchem/libsym/oriorb.F, line  198:

 OriOrb: Failure to resolve orbital degeneracies.
**************************************************
 RAS-CI total energy for state   1:   -306.196637466801
  Excitation energy (eV) =  0.000000000000
  Multiplicity: Triplet 
  Dipole Moment:   -0.0000 X     0.0000 Y    -0.4275 Z
  Amplitudes : 
  
 | HOLE  | ALPHA | BETA  | PART  |    AMPLITUDE 
--------------------------------------------------
 |       | 1100  | 0011  |       |     3.3470690850813E-01
 |       | 1010  | 1001  |       |     3.0932847034804E-01
 |       | 1010  | 0101  |       |     2.9756762997754E-01
 |       | 1001  | 1010  |       |    -3.0932847034802E-01
 |       | 1001  | 0110  |       |    -3.8717863878017E-01
 |       | 0110  | 1001  |       |     3.8717863878021E-01
 |       | 0110  | 0101  |       |    -2.2937908465369E-01
 |       | 0101  | 1010  |       |    -2.9756762997752E-01
 |       | 0101  | 0110  |       |     2.2937908465367E-01
 |       | 0011  | 1100  |       |    -3.3470690850819E-01
--------------------------------------------------
*** Contributions RASCI wfn    Active:  99.76
                                 Hole:   0.11
                                 Part:   0.14
  
 NATURAL OCCUPATION NUMBERS (higher than 1.0E-05)
            1           2           3           4           5           6
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
            7           8           9          10          11          12
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
           13          14          15          16          17          18
    1   2.0000000   2.0000000   2.0000000   1.9999998   1.9999996   1.9999994
           19          20          21          22          23          24
    1   1.9999968   1.9999955   1.9999952   1.9999942   1.9999631   1.9996040
           25          26          27          28          29          30
    1   1.9995604   1.1393807   1.0001290   0.9998572   0.8605271   0.0005405
           31          32          33          34          35
    1   0.0003054   0.0000714   0.0000426   0.0000123   0.0000119
  
  
**************************************************
 RAS-CI total energy for state   2:   -306.183766634779
  Excitation energy (eV) =  0.350233158637
  Multiplicity: Triplet 
  Dipole Moment:   -0.0000 X     0.0000 Y    -0.4050 Z
  Trans. Moment:   -0.0000 X     0.0000 Y     0.0122 Z
  Strength   :  0.000001
  Amplitudes : 
  
 | HOLE  | ALPHA | BETA  | PART  |    AMPLITUDE 
--------------------------------------------------
 |       | 1100  | 0011  |       |    -4.9827250669190E-01
 |       | 1010  | 1001  |       |     1.1094076749640E-01
 |       | 1010  | 0101  |       |    -1.7521930725883E-01
 |       | 1001  | 1010  |       |    -1.1094076749636E-01
 |       | 1001  | 0110  |       |    -4.1776182635766E-01
 |       | 0110  | 1001  |       |     4.1776182635772E-01
 |       | 0101  | 1010  |       |     1.7521930725885E-01
 |       | 0011  | 1100  |       |     4.9827250669183E-01
--------------------------------------------------
*** Contributions RASCI wfn    Active:  94.47
                                 Hole:   2.96
                                 Part:   2.57
  
 NATURAL OCCUPATION NUMBERS (higher than 1.0E-05)
            1           2           3           4           5           6
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
            7           8           9          10          11          12
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
           13          14          15          16          17          18
    1   1.9999999   1.9999996   1.9999994   1.9999985   1.9999971   1.9999949
           19          20          21          22          23          24
    1   1.9999926   1.9999762   1.9999695   1.9999154   1.9997436   1.9921757
           25          26          27          28          29          30
    1   1.9846820   1.0189454   1.0019739   1.0002726   0.9810318   0.0149786
           31          32          33          34          35          36
    1   0.0059072   0.0001834   0.0001335   0.0000609   0.0000223   0.0000134
  
  
**************************************************
 RAS-CI total energy for state   3:   -306.166970992664
  Excitation energy (eV) =  0.807265833686
  Multiplicity: Singlet 
  Dipole Moment:    0.0000 X    -0.0000 Y    -0.7068 Z
  Trans. Moment:    0.0000 X     0.0000 Y     0.0000 Z
  Strength   :  0.000000
  Amplitudes : 
  
 | HOLE  | ALPHA | BETA  | PART  |    AMPLITUDE 
--------------------------------------------------
 |       | 1010  | 1010  |       |     3.8839138300971E-01
 |       | 1010  | 0110  |       |     3.4020306004333E-01
 |       | 1001  | 1001  |       |    -2.6023743925514E-01
 |       | 1001  | 0101  |       |    -3.0959273915830E-01
 |       | 0110  | 1010  |       |     3.4020306004592E-01
 |       | 0110  | 0110  |       |    -2.4513662548918E-01
 |       | 0101  | 1001  |       |    -3.0959273916094E-01
 |       | 0101  | 0101  |       |     1.9460771412498E-01
 |  25   | 1011  | 0110  |       |    -1.3399427392223E-01
 |  25   | 0110  | 1011  |       |    -1.3399427392274E-01
 |       | 0100  | 1001  |  30   |     1.1200120894898E-01
 |       | 1001  | 0100  |  30   |     1.1200120894861E-01
--------------------------------------------------
*** Contributions RASCI wfn    Active:  73.99
                                 Hole:  14.91
                                 Part:  11.10
  
 NATURAL OCCUPATION NUMBERS (higher than 1.0E-05)
            1           2           3           4           5           6
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
            7           8           9          10          11          12
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
           13          14          15          16          17          18
    1   2.0000000   1.9999998   1.9999996   1.9999974   1.9999900   1.9999820
           19          20          21          22          23          24
    1   1.9999561   1.9999219   1.9999149   1.9998159   1.9969552   1.9852515
           25          26          27          28          29          30
    1   1.9743459   1.2094035   1.1588053   0.8491658   0.7915534   0.0225778
           31          32          33          34          35          36
    1   0.0103035   0.0014597   0.0002305   0.0001433   0.0000805   0.0000534
           37          38          39          40
    1   0.0000255   0.0000157   0.0000133   0.0000128

$comment
  RAS(4,4)-2SF-CI low-lying states of DDMX tetraradical
$end

$molecule
0 5
C           0.000000    0.000000    1.092150
C          -1.222482    0.000000    0.303960
C          -2.390248    0.000000    1.015958
H          -2.344570    0.000000    2.095067
H          -3.363161    0.000000    0.537932
C          -1.215393    0.000000   -1.155471
H          -2.150471    0.000000   -1.702536
C           0.000000    0.000000   -1.769131
C           1.215393    0.000000   -1.155471
H           2.150471    0.000000   -1.702536
C           1.222482    0.000000    0.303960
C           2.390248    0.000000    1.015958
H           2.344570    0.000000    2.095067
H           3.363161    0.000000    0.537932
$end

$rem
  jobtype           sp
  method            rasci
  basis             6-31g*
  max_scf_cycles    200
  scf_convergence 8
  !scf_algorithm     dm
  unrestricted      false         ! RASCI only works with unrestricted orbitals
scf_guess read
sym_ignore true
!RASCI
  RAS_ROOTS         10            ! Compute 9 states
  RAS_ELEC          4             ! Active electrons    (RAS2)
  RAS_ACT           4             ! Active orbitals     (RAS2)
  RAS_OCC           25            ! Doubly occ orbitals (RAS1)
  RAS_DO_HOLE       true          ! Compute hole contributions (RAS1 -> RAS2)
  RAS_DO_PART       true          ! Compute part contributions (RAS2 -> RAS3)
  RAS_SPIN_MULT     0             ! Compute any spin multiplicity
  RAS_NATORB        true          ! Compute natural orbital occupancies
! RAS_ACT_ORB       [26,27,28,29] ! Pick active orbitals
! RAS_NATORB_STATE  2             ! Save natural orbitals of state 2 in file 53.0
! RAS_GUESS_CS      1             ! Force (at least) 1 close shell guess
$end
 SCF converges when RMS gradient is below 1.0e-08
 ---------------------------------------
  Cycle       Energy        RMS Gradient
 ---------------------------------------
    1    -306.1969607827      1.22e-06   Normal BFGS step
    2    -306.1969607827      6.79e-08   Normal BFGS step
    3    -306.1969607827      4.19e-08   Normal BFGS step
    4    -306.1969607827      7.73e-09  Convergence criterion met
The disked orbital energies are calculated using alpha and beta Focks
 ---------------------------------------
 SCF time:   CPU 7.43s  wall 1.00s 
<S^2> =          6.000000000
 SCF   energy in the final basis set =     -306.1969607827
 Total energy in the final basis set =     -306.1969607827

 Q-Chem warning in module /public/home/huangxk/qchem/libsym/oriorb.F, line  198:

 OriOrb: Failure to resolve orbital degeneracies.


 Q-Chem warning in module /public/home/huangxk/qchem/libsym/oriorb.F, line  198:

 OriOrb: Failure to resolve orbital degeneracies.
**************************************************
 RAS-CI total energy for state   1:   -306.196637466808
  Excitation energy (eV) =  0.000000000000
  Multiplicity: Triplet 
  Dipole Moment:    0.0000 X     0.0000 Y    -0.4275 Z
  Amplitudes : 
  
 | HOLE  | ALPHA | BETA  | PART  |    AMPLITUDE 
--------------------------------------------------
 |       | 1100  | 0011  |       |     3.3470687858438E-01
 |       | 1010  | 1001  |       |     3.0932877827623E-01
 |       | 1010  | 0101  |       |     2.9756757814028E-01
 |       | 1001  | 1010  |       |    -3.0932877827621E-01
 |       | 1001  | 0110  |       |    -3.8717852414608E-01
 |       | 0110  | 1001  |       |     3.8717852414613E-01
 |       | 0110  | 0101  |       |    -2.2937900443102E-01
 |       | 0101  | 1010  |       |    -2.9756757814030E-01
 |       | 0101  | 0110  |       |     2.2937900443101E-01
 |       | 0011  | 1100  |       |    -3.3470687858438E-01
--------------------------------------------------
*** Contributions RASCI wfn    Active:  99.76
                                 Hole:   0.11
                                 Part:   0.14
  
 NATURAL OCCUPATION NUMBERS (higher than 1.0E-05)
            1           2           3           4           5           6
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
            7           8           9          10          11          12
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
           13          14          15          16          17          18
    1   2.0000000   2.0000000   2.0000000   1.9999998   1.9999996   1.9999994
           19          20          21          22          23          24
    1   1.9999968   1.9999955   1.9999952   1.9999942   1.9999631   1.9996040
           25          26          27          28          29          30
    1   1.9995604   1.1393814   1.0001290   0.9998572   0.8605265   0.0005405
           31          32          33          34          35
    1   0.0003054   0.0000714   0.0000426   0.0000123   0.0000119
  
  
**************************************************
 RAS-CI total energy for state   2:   -306.193360763828
  Excitation energy (eV) =  0.089163624595
  Multiplicity: Triplet 
  Dipole Moment:   -0.0000 X     0.0000 Y     0.1248 Z
  Trans. Moment:    0.0000 X     0.0135 Y    -0.0000 Z
  Strength   :  0.000000
  Amplitudes : 
  
 | HOLE  | ALPHA | BETA  | PART  |    AMPLITUDE 
--------------------------------------------------
 |       | 1100  | 1010  |       |     6.4733284925364E-01
 |       | 1100  | 0110  |       |    -1.7445488462412E-01
 |       | 1010  | 1100  |       |    -6.4732513315631E-01
 |       | 0110  | 1100  |       |     1.7448266974484E-01
 |  25   | 1011  | 1100  |       |    -1.0139032975449E-01
 |  25   | 1100  | 1011  |       |     1.0138636064193E-01
--------------------------------------------------
*** Contributions RASCI wfn    Active:  92.05
                                 Hole:   5.07
                                 Part:   2.88
  
 NATURAL OCCUPATION NUMBERS (higher than 1.0E-05)
            1           2           3           4           5           6
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
            7           8           9          10          11          12
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
           13          14          15          16          17          18
    1   2.0000000   2.0000000   1.9999999   1.9999997   1.9999992   1.9999984
           19          20          21          22          23          24
    1   1.9999979   1.9999764   1.9999758   1.9999485   1.9997480   1.9980053
           25          26          27          28          29          30
    1   1.9876997   1.9389797   0.9999403   0.9980288   0.0728014   0.0025846
           31          32          33          34          35          36
    1   0.0013129   0.0005440   0.0002359   0.0001460   0.0000256   0.0000181
           37
    1   0.0000128
  
  
**************************************************
 RAS-CI total energy for state   3:   -306.190584369951
  Excitation energy (eV) =  0.164713145829
  Multiplicity: Singlet 
  Dipole Moment:   -0.0000 X    -0.0000 Y     0.1266 Z
  Trans. Moment:   -0.0000 X     0.0000 Y     0.0000 Z
  Strength   :  0.000000
  Amplitudes : 
  
 | HOLE  | ALPHA | BETA  | PART  |    AMPLITUDE 
--------------------------------------------------
 |       | 1100  | 1010  |       |     6.4773439452054E-01
 |       | 1100  | 0110  |       |    -1.7263435762566E-01
 |       | 1010  | 1100  |       |     6.4772689052646E-01
 |       | 0110  | 1100  |       |    -1.7267377351272E-01
 |  25   | 1011  | 1100  |       |     1.0136523426430E-01
 |  25   | 1100  | 1011  |       |     1.0136477506426E-01
--------------------------------------------------
*** Contributions RASCI wfn    Active:  92.03
                                 Hole:   5.10
                                 Part:   2.87
  
 NATURAL OCCUPATION NUMBERS (higher than 1.0E-05)
            1           2           3           4           5           6
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
            7           8           9          10          11          12
    1   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000   2.0000000
           13          14          15          16          17          18
    1   2.0000000   2.0000000   1.9999999   1.9999997   1.9999975   1.9999972
           19          20          21          22          23          24
    1   1.9999964   1.9999904   1.9999715   1.9999604   1.9997453   1.9980609
           25          26          27          28          29          30
    1   1.9870187   1.9388173   0.9999035   0.9979904   0.0735297   0.0026447
           31          32          33          34          35          36
    1   0.0013223   0.0005535   0.0003081   0.0001229   0.0000310   0.0000165

References：

ddmx
ddmx1008×426 76.5 KB

#2

I cannot comment on the values in the paper, especially as it is uncertain to me if the geometry in your input, which seems to be from Example 7.164 in the Manual (7.12.15 Examples‣ 7.12 Restricted Active Space Spin-Flip (RAS-SF) and Configuration Interaction (RAS-CI) ‣ Chapter 7 Open-Shell and Excited-State Methods ‣ Q-Chem 6.2 User’s Manual), is the same that is reported in the paper.

With regards to the different RAS SF target states obtained with different number of requested roots, this is not necessarily a bug, rather a consequence of insufficient number of guess vectors being spawned before the Davidson procedure. Someone can correct me but there is no RAS keyword to set the number of guess vectors currently (unlike for EOM-CC methods, where a REM keyword such as EOM_NGUESS_SINGLES exists). So, I would suggest that you request a few more states than required to get a converged set of low-lying SF states. Say, for example, if you request 15 or 20 roots, it would include all the different SF target states that you obtain from your two separate output files.

#3

You should always request more roots than you want from any iterative diagonalization procedure, which means most excited-state methods that afford multiple roots. Otherwise, results may not be converged with respect to the size of the iterative subspace.

#4

Thanks for your suggestion! As you said, I obtained stable low-lying excitation energy data after increasing the number of calculated states.But the data is still different from the literature. Maybe, as you said, the configuration I calculated is different from the one in the paper. If so, how can I confirm whether the energy calculated by this method is reasonable?
I would be very grateful if you could give me (a beginner in quantum chemistry :smiling_face_with_tear:) some more advice.

#5

Thank you , I gained a lot.