Stokes Shift Calculator

Properties

Notes

Stokes Shift

recommended

Workflow

We estimate the Stokes shift in vacuum by subtracting energies of the first excited state \(S_1\) in \(S_0\) geometry and \(S_1\) geometry.

The computation of the Stokes shift is visualized in the following figure. The left side I) shows the energy landscapes of the \(S_0\) and \(S_1\) states and the corresponding vertical excitation (absorption) from the \(S_0\) ground state. II) shows the de(-)excitation (emission) from the relaxed \(S_1\) state. The difference is taken as the Stokes shift.

../../_images/S0S1_S1S0.png

The Stokes Shift Calculator workflow is implemented as the four separate runs of the Parametrizer Module using PySCF for quantum chemistry calculations. The last step analyzes the difference of the \(E(S_1|S_0)\) and \(E(S_1|S_1)\) and deliver the final output in eV and nm. The notations are <state>|<geometry>, where state refers to the electronic state for which the energy is evaluated, and geometry refers to the state whose equilibrium geometry is used.

Stokes Shift Workflow Overview

Nanomatch Software

Scientific Role

Illustration

Parametrizer
Geometry optimization
in \(S_0\) state
 ../../_images/parametrizer.png

Parametrizer
Geometry optimization
in \(S_1\) state
 ../../_images/parametrizer.png

Parametrizer
Excitation Energy \(S_1\):
in \(S_0\) geometry,
\(E(S_1|S_0)\)
 ../../_images/Parametrizer3.png

Parametrizer
Excitation Energy \(S_1\)
in \(S_1\) geometry,
\(E(S_1|S_1)\)
 ../../_images/Parametrizer3.png

Stokes Shift Analysis
Compute Stokes Shift as
\(E(S_1|S_0) - E(S_1|S_1)\)
 ../../_images/StokesShiftAnalysis.png

Implemented Scientific Methods

Step

Method

Optimization in \(S_0\) state

DFT, BLYP35/def2-SVP

Optimization in \(S_1\) state

TDDFT, BLYP35/def2-SVP

Excitation energy evaluation

TDDFT, M06-2X/def2-SVP

Software:

Output

Displayed Results

The data below will be displayed as the workflow ends (backend name: result.yml):

QLQHAHDIYGVQJO-UHFFFAOYSA-N:
  stokes_shift:
    results:
      E(S1,S0_opt) in eV: 2.933367648192653
      E(S1,S0_opt) in nm: 422.72232761686246
      E(S1,S1_opt) in eV: 2.244059764534579
      E(S1,S1_opt) in nm: 552.5699536158199
      Stokes shift in eV: 0.6893078836580742
      Stokes shift in nm: -129.84762599895748
    value: 0.6893078836580742

These represent the Stokes Shift and the excitation energies used to compute it in various units.

Files

In addition to parsed output, the following files are available upon the workflow completion:

No.

File

Description

1

Molecule_S0_opt.mol2

Ground State (\(S0\)) geometry in MOL2 format

2

Molecule_S1_opt.mol2

Excited state (\(S1\)) geometry in MOL2 format

Benchmarks

Benchmark Set

To ensure, the accuracy of this workflow, we selected two experimentally studied Stokes shifts from Ref. [1], [2] and compared them with our theoretically calculated Stokes shift results, as presented below.

../../_images/tp-bodipy-summary-structure.png

Experimental verification

The following table shows the published experimental data and the results of the workflow above.

../../_images/Results.png

References