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7.3 Time-Dependent Density Functional Theory (TDDFT)

7.3.3 Job Control for TDDFT

(December 20, 2021)

Input for time-dependent density functional theory calculations follows very closely the input already described for the uncorrelated excited state methods described in the previous section (in particular, see Section 7.2.8). There are several points to be aware of:

  • The exchange and correlation functionals are specified exactly as for a ground state DFT calculation, through EXCHANGE and CORRELATION.

  • If RPA is set to TRUE, a “full” TDDFT calculation will be performed, however the default value is RPA = FALSE, which invokes the TDA, 470 Hirata S., Head-Gordon M.
    Chem. Phys. Lett.
    (1999), 314, pp. 291.
    Link
    in which the de-excitation amplitudes 𝐘 in Eq. (7.15) are neglected, which is usually a good approximation for excitation energies, although oscillator strengths within the TDA no longer formally satisfy the Thomas-Reiche-Kuhn sum rule. For RPA = TRUE, a TDA calculation is performed first and used as the initial guess for the full TDDFT calculation. The TDA calculation can be skipped altogether using RPA = 2

  • If SPIN_FLIP is set to TRUE when performing a TDDFT calculation, a SF-DFT calculation will also be performed. At present, SF-DFT is only implemented within TDDFT/TDA so RPA must be set to FALSE. Remember to set the spin multiplicity to 3 for systems with an even-number of electrons (e.g., diradicals), and 4 for odd-number electron systems (e.g., triradicals).

  • If MGGA_GINV is set to 1 when performing a TDDFT calculation, gauge invariance correction will be added to MGGA functionals. 68 Bates J. E., Furche F.
    J. Chem. Phys.
    (2012), 137, pp. 164105.
    Link

TRNSS

TRNSS
       Controls whether reduced single excitation space is used.
TYPE:
       LOGICAL
DEFAULT:
       FALSE Use full excitation space.
OPTIONS:
       TRUE Use reduced excitation space.
RECOMMENDATION:
       None

TRTYPE

TRTYPE
       Controls how reduced subspace is specified.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       1 Select orbitals localized on a set of atoms. 2 Specify a set of orbitals. 3 Specify a set of occupied orbitals, include excitations to all virtual orbitals.
RECOMMENDATION:
       None

MGGA_GINV

MGGA_GINV
       Controls whether to add gauge invariance correction to MGGA functionals.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 No correction. 1 Add gauge invariance correction to MGGA functionals.
RECOMMENDATION:
       Not recommended when TDA is used because TDA has broken gauge invariance.

N_SOL

N_SOL
       Specifies number of atoms or orbitals in the $solute section.
TYPE:
       INTEGER
DEFAULT:
       No default.
OPTIONS:
       User defined.
RECOMMENDATION:
       None

CISTR_PRINT

CISTR_PRINT
       Controls level of output.
TYPE:
       LOGICAL
DEFAULT:
       FALSE Minimal output.
OPTIONS:
       TRUE Increase output level.
RECOMMENDATION:
       None

CUTOCC

CUTOCC
       Specifies occupied orbital cutoff.
TYPE:
       INTEGER
DEFAULT:
       50
OPTIONS:
       0-200 CUTOFF = CUTOCC/100
RECOMMENDATION:
       None

CUTVIR

CUTVIR
       Specifies virtual orbital cutoff.
TYPE:
       INTEGER
DEFAULT:
       0 No truncation
OPTIONS:
       0-100 CUTOFF = CUTVIR/100
RECOMMENDATION:
       None

PBHT_ANALYSIS

PBHT_ANALYSIS
       Controls whether overlap analysis of electronic excitations is performed.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Do not perform overlap analysis. TRUE Perform overlap analysis.
RECOMMENDATION:
       None

PBHT_FINE

PBHT_FINE
       Increases accuracy of overlap analysis.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       FALSE TRUE Increase accuracy of overlap analysis.
RECOMMENDATION:
       None

SRC_DFT

SRC_DFT
       Selects form of the short-range corrected functional.
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       1 SRC1 functional. 2 SRC2 functional.
RECOMMENDATION:
       None

OMEGA

OMEGA
       Sets the Coulomb attenuation parameter for the short-range component.
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       n Corresponding to ω=n/1000, in units of bohr-1
RECOMMENDATION:
       None

OMEGA2

OMEGA2
       Sets the Coulomb attenuation parameter for the long-range component.
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       n Corresponding to ω2=n/1000, in units of bohr-1
RECOMMENDATION:
       None

HF_SR

HF_SR
       Sets the fraction of Hartree-Fock exchange at r12=0.
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       n Corresponding to HF_SR = n/1000
RECOMMENDATION:
       None

HF_LR

HF_LR
       Sets the fraction of Hartree-Fock exchange at r12=.
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       n Corresponding to HF_LR = n/1000
RECOMMENDATION:
       None

WANG_ZIEGLER_KERNEL

WANG_ZIEGLER_KERNEL
       Controls whether to use the Wang-Ziegler non-collinear exchange-correlation kernel in a SF-DFT calculation. Set NEW_DFT = true if using a Q-Chem version older than 5.0.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Do not use non-collinear kernel. TRUE Use non-collinear kernel.
RECOMMENDATION:
       None

SET_CISGUES

SET_CISGUES
       Controls how to generate the initial guess excitation vectors in CIS/TDA/RPA calculations.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Generate N (no. of roots requested) occupiedvirtual single orbital transitions according to their orbital energy difference order (from low to high). This is the common scenario. 1 Generate N-1 occupiedvirtual single orbital transitions according to their orbital energy difference order (from low to high), and generate another guess excitation vector consist of all the remaining single orbital transitions in the occupiedvirtual transition space with equal weights. 2 Generate N occupied/virtual single orbital transitions according to their orbital energy difference order (from low to high), and generate one more guess excitation vector consist of all the remaining single orbital transitions in the occupiedvirtual transition space with equal weights.
RECOMMENDATION:
       The default setting should work for most of the cases. However, when the no. of roots is small, in some CIS/TDA/RPA calculations low energy excited states could be missing. The options SET_CISGUES = 1 or 2 may remedy this root missing issue by sampling more vectors in the transition space. Setting SET_CISGUES = 1 or 2 may take more cycles to converge in the Davidson iteration, but the results are expected to be more reliable. Currently SET_CISGUES = 1 or 2 are not supported in SF-XCIS calculations. Setting TRNSS = TRUE also disables the setting of SET_CISGUES.