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7.7 Non-Orthogonal CIS and Static Exchange (STEX)

7.7.4 Job Control

(September 1, 2024)

NOCIS, 1C-NOCIS, and STEX run as subroutines in GEN_SCFMAN. Thus, for all calculations, you must set GEN_SCFMAN = TRUE. It is also highly recommended that you run an open-shell ground state calculation prior to running your NOCIS/STEX/1C-NOCIS calculations, which are all restricted.

NOCIS

NOCIS
       Requests a NOCIS/STEX/1C-NOCIS/EA-TDDFT calculation.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Do not run these methods. TRUE Run one of these methods, options controlled in $nocis.
RECOMMENDATION:
       None

Options below this line are set within the $nocis section.

STEX
       Run a STEX calculation
INPUT SECTION: $nocis
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       The presence of this keyword will activate STEX.
RECOMMENDATION:
       None

ONE_CENTER
       Run a 1C-NOCIS calculation
INPUT SECTION: $nocis
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       False Run a NOCIS calculation. True Run a 1C-NOCIS calculation.
RECOMMENDATION:
       None

ORB_OFFSET
       Determines the starting orbital for a NOCIS/STEX/1C-NOCIS/EA-TDDFT calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       NONE
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Set according to the first orbital of interest in the system in question. For example, this would be set to 0 for the O K-edge in CO2 because the two O 1s orbitals lie below the C 1s, so for the C K-edge this would be set to 2.

NUM_REF
       Sets the number of reference orbitals in a NOCIS/STEX/1C-NOCIS/EA-TDDFT calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       NONE
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Set according to the number of consecutive orbitals of interest for the calculation. For example, for the oxygen K-edge in CO2, the number of references would be 2 (two O 1s orbitals), whereas for the carbon K-edge it would be 1 (one C 1s).

Options below this line are exclusive to 1C-NOCIS calculations for 2eOS references.

OS_IS
       Triggers a 1C-NOCIS calculation with an MS = 0 open-shell initial state (IS).
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       ROKS
OPTIONS:
       CIS Employ a CIS excited-state wave function transformed into the NTO basis as the IS ROKS Employ a ROKS- or ROHF-optimized wave function (singlets or triplets) as the IS CIS_ROKS Use CIS NTOs as a guess for an RO calculation on the IS.
RECOMMENDATION:
       Use CIS when targeting a well-defined initial state. Else use ROSCF. Note that, if the CIS_ROKS option is used, the previous excited state job can employ TDDFT instead of CIS to provide a better guess.

OS_IS_CIS_STATE
       When using CIS or CIS_ROKS for OS_IS, specifies which CIS state to target.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Set according to the desired CIS state.

OS_IS_OCC_VALENCE
       When using ROKS for OS_IS, specifies which occupied orbital to excite from.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       HOMO
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Set according to the desired ROKS state. This is a 0-indexed variable (the lowest orbital has index 0).

OS_IS_VIR_VALENCE
       When using ROKS for OS_IS, specifies which virtual orbital to excite into.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       LUMO
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Set according to the desired ROKS state. This is a 0-indexed variable (the lowest orbital has index 0).

OS_IS_SCF_ALGORITHM
       When using ROKS for OS_IS, specifies the SCF algorithm for convergence of the IS.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       GDM when OS_IS_CIS_STATE = 1 or IS_OCC_VALENCE = HOMO and IS_VIR_VALENCE = LUMO SGM otherwise
OPTIONS:
       DIIS GDM GDM_LS SGM SGM_LS
RECOMMENDATION:
       Use defaults.

OS_IS_DSCF_ALGORITHM
       When using ROKS for OS_IS, specifies the SCF algorithm for convergence of the IS.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       NONE
OPTIONS:
       MOM IMOM STEP STEP_MOM
RECOMMENDATION:
       When using DIIS, MOM or IMOM may be necessary to target higher valence excited states.

OS_IS_SCF_CONVERGENCE
       When using ROKS or CIS_ROKS for OS_IS, specifies the SCF convergence for the IS ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       7 for SGM- and GDM-based solvers 8 otherwise
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Modify as needed for convergence, but thresholds below 5 for descent-based methods (GDM, SGM), and 7 for others may provide unsufficiently-converged orbitals.

OS_IS_SGM_GRADIENT
       When using SGM for OS_IS_SCF_ALGORITHM, specifies the DELTA_GRADIENT_SCALE for the IS ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       75 when using SGM as the SCF solver for the initial valence state NONE otherwise
OPTIONS:
       n Positive integer below 100
RECOMMENDATION:
       See DELTA_GRADIENT_SCALE $rem variable. If ROKS_IS_SS_MIXING is set to FALSE, try the default. Otherwise, a value of around 10 might be required. If its converging to the wrong state, try decreasing.

OS_IS_SS_MIXING
       Controls whether to allow mixing between the singly-occupied orbitals during the ROKS procedure.
INPUT SECTION: $nocis
TYPE:
       BOOL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Supress coupling. TRUE Allow coupling.
RECOMMENDATION:
       See ROKS_SS_MIXING $rem variable. Supressing coupling is useful when the resuling states are difficult to converge and / or overlap significantly with the ground state, and seems to be harmless otherwise. Certain ππ* excitated states are particularly susceptible to this (Example 7.8.3). Only works with descent-based solvers (GDM or SGM).

OS_FS_REFERENCE_ORB
       Choice of reference orbitals for the final states (FS)
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       ROKS_2EOS for singlet valence excited states QUARTET_ION for triplet valence excited states
OPTIONS:
       OC_NOCIS Uses ROSCF doublet core ion orbitals, rotated into the closed-shell 1C-NOCIS NTO basis QUARTET_ION Uses the ROSCF quartet core ion orbitals ROKS_2EOS Uses the |1Φot orbitals optimized via ROKS.
RECOMMENDATION:
       Use defaults.

OS_FS_NS_REFERENCE
       Specifies a single common reference to use for all core orbitals when NUM_REF > 1.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       NONE
OPTIONS:
       n Non-negative integer
RECOMMENDATION:
       Experimental feature. When simulating, say, the M2, 3-edge of an iron compound, the 3s core hole reference may be useful - while it doesn’t optimize each individual 3p core hole individually, it partially captures core hole orbital realxation and provides an unbiased reference for the set of three 3p orbitals. Note no spin-orbit coupling is implemented at the moment for these calculations.

OS_FS_D_ION_SCF_ALGORITHM
       Specifies the SCF algorithm for convergence of the doublet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       DIIS
OPTIONS:
       DIIS SGM SGM_LS
RECOMMENDATION:
       Use default. If convergence is not possible, try SGM.

OS_FS_D_ION_DSCF_ALGORITHM
       Specifies the SCF algorithm for convergence of the doublet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       MOM when OS_FS_D_ION_SCF_ALGORITHM = DIIS NONE otherwise
OPTIONS:
       MOM IMOM STEP STEP_MOM
RECOMMENDATION:
       None.

OS_FS_D_ION_SCF_CONVERGENCE
       Specifies the SCF convergence for the doublet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       ijk Positive integer. i, j, k, … relate to reference 1, 2, 3, …
RECOMMENDATION:
       Setting this $rem variable to 0 skips the doublet core ion calculations and instead uses the valence excited state orbitals as a guess for either the quartet core ion ROHF calculation or |1Φot ROKS calculations. When that fails to converge the reference orbitals, attempt to use doublet core ion orbitals as a guess. Thresholds below 5 for SGM-Based solvers, or 7 for DIIS / MOM may provide insufficiently converged orbitals. This may not be as critical (and perhaps necessar) if just using them as a guess for subsequent calculations. Note DFT orbitals may serve as better guess - specify the desired functional via the ENV_METHOD $rem variable. When using closed-shell 1C-NOCIS reference orbitals for the 1C-NOCIS 2eOS calculation, proper convergence and not DFT must be used.

OS_FS_D_ION_SGM_GRADIENT
       When using SGM for OS_FS_D_ION_SCF_ALGORITHM, specifies the DELTA_GRADIENT_SCALE for the doublet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       NONE
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Anecdotically, a value of 1 - 10 seems to work well for core ions. If the ROSCF calculation is not converging, try increasing.

OS_FS_Q_ION_SCF_ALGORITHM
       Specifies the SCF algorithm for convergence of the quartet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       DIIS
OPTIONS:
       DIIS SGM SGM_LS
RECOMMENDATION:
       Use DIIS when possible. For problematic cases, use SGM.

OS_FS_Q_ION_DSCF_ALGORITHM
       Specifies the SCF algorithm for convergence of the quartet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       MOM when OS_FS_D_ION_SCF_ALGORITHM = DIIS NONE otherwise
OPTIONS:
       MOM IMOM STEP STEP_MOM
RECOMMENDATION:
       For efficiency, attempt using MOM, IMOM, STEP, or STEP_MOM first (requires DIIS for OS_FS_Q_ION_SCF_ALGORITHM). If the SCF procedure fails to converge or converges to the wrong state, do not set this rem variable and attempt using SGM in OS_FS_Q_ION_SCF_ALGORITHM.

OS_FS_Q_ION_SCF_CONVERGENCE
       Specifies the SCF convergence for the quartet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       6 (for each reference) for SGM-based solvers 8 (for each reference) otherwise.
OPTIONS:
       ijk Positive integer. i, j, k, … relate to reference 1, 2, 3, …
RECOMMENDATION:
       Modify as needed for convergence, but thresholds below 5 for SGM-based methods, and 7 for others may provide unsufficiently-converged orbitals.

OS_FS_Q_ION_SGM_GRADIENT
       When using SGM for OS_FS_Q_ION_SCF_ALGORITHM, specifies the DELTA_GRADIENT_SCALE for the quartet core ion ROSCF calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       NONE
OPTIONS:
       n Positive integer
RECOMMENDATION:
       Anecdotically, a value of 1 - 10 seems to work well for core ions. If the ROSCF calculation is not converging, try increasing.

OS_FS_2EOS_SCF_ALGORITHM
       Specifies the SCF algorithm for convergence of the |1Φot ROKS calculation.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       SGM
OPTIONS:
       DIIS SGM SGM_LS
RECOMMENDATION:
       Use DIIS for very simple (small) molecules and low-lying valence excited states. Else, use SGM.

OS_FS_2EOS_DSCF_ALGORITHM
       Specifies the SCF algorithm for convergence of the |1Φot ROKS calculation.
INPUT SECTION: $nocis
TYPE:
       STRING
DEFAULT:
       MOM when OS_FS_D_ION_SCF_ALGORITHM = DIIS NONE otherwise
OPTIONS:
       MOM IMOM STEP STEP_MOM
RECOMMENDATION:
       Use defaults.

OS_FS_2EOS_SCF_CONVERGENCE
       Specifies the SCF convergence for the |1Φot ROKS calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       6 (for each reference) for SGM-based solvers 8 (for each reference) otherwise.
OPTIONS:
       ijk Positive integer. i, j, k, … relate to reference 1, 2, 3, …
RECOMMENDATION:
       Modify as needed for convergence, but thresholds below 5 for SGM-based methods, and 7 for others may provide unsufficiently-converged orbitals.

OS_FS_2EOS_SGM_GRADIENT
       When using SGM for OS_FS_2EOS_SCF_ALGORITHM, specifies the DELTA_GRADIENT_SCALE for the |1Φot core- excited ROKS calculation.
INPUT SECTION: $nocis
TYPE:
       INTEGER
DEFAULT:
       75 when ROKS_FS_2EOS_SS_MIXING is set to FALSE 5 otherwise
OPTIONS:
       n Positive integer below 100
RECOMMENDATION:
       See DELTA_GRADIENT_SCALE $rem variable. If ROKS_FS_2EOS_SS_MIXING is set to FALSE, try the default. Otherwise, a value of around 1 - 10 might be required. If its converging to the wrong state, try decreasing.

OS_FS_2EOS_SS_MIXING
       Controls whether to allow mixing between the singly-occupied orbitals during the ROKS procedure.
INPUT SECTION: $nocis
TYPE:
       BOOL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Supress coupling. TRUE Allow coupling.
RECOMMENDATION:
       See ROKS_SS_MIXING $rem variable. Supressing coupling is useful when the resuling states are difficult to converge and / or overlap significantly with the ground state, and seems to be harmless otherwise. 1s3s excited states, for example, are particularly susceptible to this phenomena. Only works with descent-based solvers (GDM or SGM).

Example 7.38  NOCIS for the nitrogen K-edge of N2

$molecule
   0 1
   N     0.000000     0.000000     0.564990
   N     0.000000     0.000000    -0.564990
$end

$rem
   METHOD           hf
   BASIS            sto-3g
   UNRESTRICTED     false
   GEN_SCFMAN       true
   NOCIS            true
   THRESH           14
   MAX_SCF_CYCLES   500
   INTEGRAL_SYMMETRY false
   POINT_GROUP_SYMMETRY false
$end

! the default behavior is NOCIS
$nocis
   ORB_OFFSET       0
   NUM_REF          2
$end

Example 7.39  STEX for the carbon K-edge of CN

$molecule
   0 2
   C  0.0000000   0.0000000  -0.6258140
   N  0.0000000   0.0000000   0.5364120
$end

$rem
   METHOD            hf
   BASIS             sto-3g
   SCF_GUESS         core
   SCF_ALGORITHM     diis_gdm
   MAX_SCF_CYCLES    5000
   THRESH            14
   SCF_CONVERGENCE   10
   INTEGRAL_SYMMETRY false
   POINT_GROUP_SYMMETRY false
$end

@@@

$molecule
read
$end

$rem
   METHOD            hf
   BASIS             sto-3g
   SCF_GUESS         read
   UNRESTRICTED      false
   SCF_ALGORITHM     diis_gdm
   GEN_SCFMAN        true
   NOCIS             true
   MAX_SCF_CYCLES    5000
   THRESH            14
   SCF_CONVERGENCE   10
   INTEGRAL_SYMMETRY    false
   POINT_GROUP_SYMMETRY false
$end

$nocis
   STEX
   ORB_OFFSET        1
   NUM_REF           1
$end

Example 7.40  1C-NOCIS for the oxygen K-edge of O2

$molecule
   0 3
   O    0.0000000   0.0000000    0.6021380
   O    0.0000000   0.0000000   -0.6021380
$end

$rem
   METHOD           hf
   BASIS            sto-3g
   GEN_SCFMAN       true
   THRESH           14
   MAX_SCF_CYCLES   500
   INTEGRAL_SYMMETRY false
   POINT_GROUP_SYMMETRY false
$end

@@@

$molecule
read
$end

$rem
   UNRESTRICTED     false
   SCF_GUESS        read
   METHOD           hf
   BASIS            sto-3g
   GEN_SCFMAN       true
   NOCIS            true
   THRESH           14
   MAX_SCF_CYCLES   500
   INTEGRAL_SYMMETRY false
   POINT_GROUP_SYMMETRY false
$end

$nocis
   ONE_CENTER
   ORB_OFFSET       0
   NUM_REF          2
$end

Example 7.41  1C-NOCIS 2eOS for the oxygen K-edge of the first singlet excited state of water. A CIS calculation on is used to provide a guess for the ROKS optimization of the target valence state.

$comment
  CIS calculation on water to generate the target initial state.
$end

$molecule
  0   1
  O   0.0000      0.0000      0.1173
  H   0.0000      0.7572     -0.4692
  H   0.0000     -0.7572     -0.4692
$end

$rem
  METHOD               HF
  UNRESTRICTED         FALSE
  BASIS                DEF2-SVP
  SYMMETRY             FALSE
  SYM_IGNORE           TRUE
  GEN_SCFMAN           TRUE
  SCF_ALGORITHM        DIIS_GDM
  CIS_N_ROOTS          3
  CIS_SINGLETS         TRUE
  CIS_TRIPLETS         FALSE
  REL_X2C              TRUE
  THRESH               14
  MEM_TOTAL            1000
  MEM_STATIC           100
  NTO_PAIRS            3
$end

@@@

$comment
  1C-NOCIS 2eOS singlet calculation.
$end

$molecule
  read
$end

$rem
  METHOD               HF
  UNRESTRICTED         FALSE
  BASIS                DEF2-SVP
  SYMMETRY             FALSE
  SYM_IGNORE           TRUE
  GEN_SCFMAN           TRUE
  SCF_GUESS            READ
  MAX_SCF_CYCLES       0
  REL_X2C              TRUE
  NOCIS                1
  THRESH               14
  MEM_TOTAL            1000
  MEM_STATIC           100
$end

$nocis
  SINGLETS
  ONE_CENTER
  OS_IS                CIS ! Use CIS NTOs for the valence excited state (IS)
$end

Example 7.42  1C-NOCIS 2eOS for the nitrogen K-edge of the first singlet excited state of pyrazine. The canonical orbitals are used as a guess for the ROKS optimization of the target valence state.

$comment
  1C-NOCIS 2eOS singlet calculation on pyrazine for the lowest excited state.
$end

$molecule
  0   1
  N   0.0000      0.0000      1.3814
  N   0.0000      0.0000     -1.3814
  C   0.0000      1.1192      0.6914
  C   0.0000     -1.1192      0.6914
  C   0.0000     -1.1192     -0.6914
  C   0.0000      1.1192     -0.6914
  H   0.0000      2.0412      1.2411
  H   0.0000     -2.0412      1.2411
  H   0.0000     -2.0412     -1.2411
  H   0.0000      2.0412     -1.2411
$end

$rem
  METHOD               HF
  UNRESTRICTED         FALSE
  BASIS                STO-3G
  SYMMETRY             FALSE
  SYM_IGNORE           TRUE
  GEN_SCFMAN           TRUE
  REL_X2C              TRUE
  NOCIS                1
  THRESH               14
  MEM_TOTAL            1000
  MEM_STATIC           100
$end

$nocis
  SINGLETS
  ONE_CENTER
  LOCALIZE_ORBITALS              2         ! Localize the two nitrogen 1s orbitals
  NUM_REF                        2         ! Two nitrogen atoms
  OS_IS                          ROKS      ! Use ROKS for the valence excited state (IS)
$end

Example 7.43  1C-NOCIS 2eOS for the oxygen K-edge of the triplet ground state of molecular oxygen. The default reference orbitals for triplets are the quartet core ion orbtials. Note it begins from a closed-shell job.

$comment
  1C-NOCIS 2eOS triplet calculation. Note we begin from a closed-shell reference.
$end

$molecule
  0   1
  O   0.0000      0.0000      0.60375
  O   0.0000      0.0000     -0.60375
$end

$rem
  METHOD               HF
  UNRESTRICTED         FALSE
  BASIS                STO-3G
  SYMMETRY             FALSE
  SYM_IGNORE           TRUE
  GEN_SCFMAN           TRUE
  SCF_ALGORITHM        DIIS_GDM
  REL_X2C              TRUE
  NOCIS                1
  THRESH               14
  MEM_TOTAL            1000
  MEM_STATIC           100
$end

$nocis
  TRIPLETS                            ! Activate a triplet 2eOS reference
  ONE_CENTER                          ! One-center approximation
  LOCALIZE_ORBITALS              2    ! Localize 2 orbitals
  NUM_REF                        2    ! Two oxygen atoms
  OS_IS                          ROKS ! Use ROHF to converge the valence excited state (IS)
  OS_FS_Q_ION_SCF_CONVERGENCE    88   ! Convergence of the quartet core ion orbitals
$end