In order to investigate the time-dependent dynamics of large, strongly correlated systems starting from the ground state,
and with a focus on minimizing computational complexity,
Hung-Yi Tsai and Prof. Jeng-Da Chai have extended thermally-assisted-occupation density functional theory (TAO-DFT)
210
J. Chem. Phys.
(2012),
136,
pp. 154104.
Link
to real-time TAO-DFT (RT-TAO).
1283
Molecules
(2023),
28,
pp. 7247.
Link
The RT-TAO method is initiated with a TAO-DFT calculation (refer to Section 5.12.3) and is followed by time propagation (refer to Section 7.4).
The computational cost associated with RT-TAO is comparable to that of time-dependent Kohn-Sham,
and it becomes equivalent to the cost of time-dependent Kohn-Sham in the absence of significant static correlation effects.
To perform an RT-TAO calculation, users are instructed to set TAO_DFT = TRUE and TDKS = TRUE in the $rem input section. Additional job control options are detailed in Section 5.12.3 and Section 7.4.2.
RT-TAO, serving as a real-time extension of TAO-DFT, is governed by a fictitious temperature parameter denoted as .
Setting TAO_DFT_THETA = 0 brings the method back to the ordinary time-dependent Kohn-Sham.
1283
Molecules
(2023),
28,
pp. 7247.
Link
In the adiabatic approximation, alongside the exchange-correlation (XC) functional, an additional functional is required for RT-TAO.
Two illustrative examples of RT-TAO calculations are provided:
Example 7.31 RT-TAO-ALDA, spin-restricted calculation on stretched H
$molecule 0 1 H 0.000000 0.000000 1.000000 H 0.000000 0.000000 -1.000000 $end $rem BASIS 6-31G* EXCHANGE gen TDKS true SCF_CONVERGENCE 7 TAO_DFT true TAO_DFT_THETA 40 ! theta = 40 mhartree TAO_DFT_THETA_NDP 3 ! default $end $xc_functional X S 1.0 C PW92 1.0 X ETheta_LDA 1.0 $end $tdks DT 0.05 MAXITER 10 ! for production, want a much larger value PROPAGATOR MMUT FIELD_VECTOR 1 1 1 FIELD_TYPE delta FIELD_AMP 0.0001 $end
Example 7.32 RT-TAO-ALDA, spin-unrestricted calculation on stretched H
$molecule 0 1 H 0.000000 0.000000 1.000000 H 0.000000 0.000000 -1.000000 $end $rem UNRESTRICTED true BASIS 6-31G* EXCHANGE gen TDKS true SCF_CONVERGENCE 7 TAO_DFT true TAO_DFT_THETA 40 ! theta = 40 mhartree TAO_DFT_THETA_NDP 3 ! default SCF_GUESS gwh SCF_GUESS_MIX 3 ! mix in 30% LUMO in alpha to break symmetry $end $xc_functional X S 1.0 C PW92 1.0 X ETheta_LDA 1.0 $end $tdks DT 0.05 MAXITER 10 ! for production, want a much larger value PROPAGATOR MMUT FIELD_VECTOR 1 1 1 FIELD_TYPE delta FIELD_AMP 0.0001 $end