7.3.3 Job Control for TDDFT‣ 7.3 Time-Dependent Density Functional Theory (TDDFT) ‣ Chapter 7 Open-Shell and Excited-State Methods ‣ Q-Chem 5.2 User’s Manual

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 7.2.7). 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,³⁸¹ in which the de-excitation amplitudes $\mathbf{Y}$ 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.¹⁵³ 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).

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
       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

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

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

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

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

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

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

OMEGA2
       Sets the Coulomb attenuation parameter for the long-range component.
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       $n$ Corresponding to $\omega 2=n/1000$ , in units of bohr ${}^{-1}$
RECOMMENDATION:
       None

HF_SR
       Sets the fraction of Hartree-Fock exchange at $r_{12}=0$ .
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       $n$ Corresponding to HF_SR = $n/1000$
RECOMMENDATION:
       None

HF_LR
       Sets the fraction of Hartree-Fock exchange at $r_{12}=\infty$ .
TYPE:
       INTEGER
DEFAULT:
       No default
OPTIONS:
       $n$ Corresponding to HF_LR = $n/1000$
RECOMMENDATION:
       None

WANG_ZIEGLER_KERNEL
       Controls whether to use the Wang-Ziegler non-collinear exchange-correlation kernel in a SF-DFT calculation.
TYPE:
       LOGICAL
DEFAULT:
       FALSE
OPTIONS:
       FALSE Do not use non-collinear kernel. TRUE Use non-collinear kernel.
RECOMMENDATION:
       None

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7.3.3 Job Control for TDDFT