Questions tagged [td-dft]
Questions related to Time-dependent density functional theory (TDDFT) is a quantum mechanical theory used in physics and chemistry to investigate the properties and dynamics of many-body systems in the presence of time-dependent potentials.
20
questions
0
votes
0
answers
31
views
Calculating charge transfer length in TDDFT calculation - Checking for charge transfer states
I am calculating conjugated organic systems using vertical excitation TD-DFT in Gaussian 16.
My specific command is
CAM-B3LYP/6-311+G(d,p) scrf=(cpcm,solvent=water) guess=check geom=check TD=(Nstates=...
- 9
5
votes
0
answers
157
views
N2 HOMO-LUMO Gap calculation
I am thinking about calculating the HOMO-LUMO energy gap for $\ce{N2}$ molecule.
I thought I could model this as a particle in a box problem to find $E_\text{HOMO}$ and $E_\text{LUMO}$.
The formula I ...
- 151
1
vote
1
answer
103
views
Open shell TDDFT excitaion contribution
If I have a open shell system (10 alpha electrons and 9 beta electrons) and running TDDFT calculations, is it possible to have a 9a→10b transition? Or does it have to be 9b→10b? Because both exciation ...
- 21
7
votes
0
answers
173
views
Changing the level of theory for organometallic compounds
I'm finishing my Ph.D. in Inorganic Chemistry and having a debate with my supervisor. The work in question have two organometallic compounds A and B. The structures are based on X-Ray Diffraction, so ...
- 485
7
votes
1
answer
2k
views
Oscillator Strength and Absorption Intensity in TDDFT
When I run a linear-response time-dependent DFT calculation in my favourite electronic structure program, for each excitation I'm given an oscillator strength, $f_i$, and transition dipole moment $$\...
- 1,929
1
vote
0
answers
127
views
How to retrieve excited state molecular orbital coefficients in Gaussian?
Currently I am doing TD-DFT calculations in Gaussian and want to calculate transition dipole moment for $S_1$ transition manually. However, I do not manage to retrieve molecular orbital coefficients ...
- 77
3
votes
1
answer
483
views
Is it rigorous enough to change a DFT functional after geometry optimization to calculate excited state properties?
I have done the geometry optimization with the B3LYP functional, however, there is a need to calculate the excited state energy, so the CAM-B3LYP functional should be better suited for that. Do I need ...
- 77
4
votes
1
answer
2k
views
Absorption and emission at same wavelength?
Is it possible for a molecule to absorb and emit at the same wavelength? What is the reason behind it?
I’m working on charged tin porphyrins and got the excitation and emission (fluorescence) ...
- 49
7
votes
2
answers
2k
views
High-temperature DFT
Why is it so difficult to perform DFT calculations that consider temperature?
I have seen that time-dependent DFT is needed to model systems at high temperature.
Why is this the case? What about ...
- 402
6
votes
1
answer
148
views
Is there an anisotropy factor (g factor) for TDDFT Abs and CD calculations?
Experimentally, anisotropy factor is calculated by dividing the CD spectra by the absorbance spectra multiplying by a factor of 32980 (in order to get a nondimensional quantity)
Theoretical ...
- 251
9
votes
0
answers
389
views
Can you explain DFT and TDDFT functioning (math aside)? [closed]
I have been recently reading a lot on the quantum mechanical theory regarding Density Functional Theory, DFT, and Time Dependent Density Functional Theory, TDDFT (Oscillatory and Rotatory Strengths in ...
- 251
6
votes
1
answer
3k
views
Is there a relation between transition density and density differences?
When I have an excited state, is there a relation between the transition density associated with this electronic transition and the density difference between the excited state density and the ground ...
- 387
9
votes
2
answers
2k
views
Excited-states properties with traditional density functional theory
Recently I was shown the book "Density Functional Theory II, Relativistic and Time Dependent Extensions" by Nalewajski in which a chapter from E. K. U. Gross et al. is printed. [1] This chapter ...
7
votes
1
answer
4k
views
Calculating singlet-triplet gap and open-shell singlet character
I am trying to calculate the singlet-triplet energy gap ($S_0-T_1$) of a conjugated system (18 atoms). For the singlet $S_0$ state, assumed to be closed shell, the Gaussian options were
...
- 314
27
votes
0
answers
3k
views
How to calculate transition dipole moment from two known wavefunctions
I'm interested in calculating the transition dipole moment (TDM) from the information from two wavefunctions of different states. This is somewhat similar to calculating the molecular dipole moment ...
- 312