10.1021/acs.jctc.9b01127.s002
Diptarka Hait
Diptarka
Hait
Martin Head-Gordon
Martin
Head-Gordon
Excited State Orbital Optimization
via Minimizing
the Square of the Gradient: General Approach and Application to Singly
and Doubly Excited States via Density Functional Theory
American Chemical Society
2020
costs 3 times
state DFT methods
approach
square gradient minimization
Excited State Orbital Optimization
determinant Δ SCF
Doubly Excited States
ground state
Density Functional Theory
SGM
Rydberg states
ROKS
TDDFT
2020-02-14 23:03:31
Dataset
https://acs.figshare.com/articles/dataset/Excited_State_Orbital_Optimization_via_Minimizing_the_Square_of_the_Gradient_General_Approach_and_Application_to_Singly_and_Doubly_Excited_States_via_Density_Functional_Theory/11858019
We
present a general approach to converge excited state solutions
to <i>any</i> quantum chemistry orbital optimization process,
without the risk of variational collapse. The resulting square gradient
minimization (SGM) approach only requires analytic energy/Lagrangian
orbital gradients and merely costs 3 times as much as ground state
orbital optimization (per iteration), when implemented via a finite
difference approach. SGM is applied to both single determinant ΔSCF
and spin-purified restricted open-shell Kohn–Sham (ROKS) approaches
to study the accuracy of orbital optimized DFT excited states. It
is found that SGM can converge challenging states where the maximum
overlap method (MOM) or analogues either collapse to the ground state
or fail to converge. We also report that ΔSCF/ROKS predict highly
accurate excitation energies for doubly excited states (which are
inaccessible via TDDFT). Singly excited states obtained via ROKS are
also found to be quite accurate, especially for Rydberg states that
frustrate (semi)local TDDFT. Our results suggest that orbital optimized
excited state DFT methods can be used to push past the limitations
of TDDFT to doubly excited, charge-transfer, or Rydberg states, making
them a useful tool for the practical quantum chemist’s toolbox
for studying excited states in large systems.