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.

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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 ...
kevin Tah N.'s user avatar
1 vote
1 answer
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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 ...
palpitate3's user avatar
7 votes
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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 ...
HCSthe2nd's user avatar
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7 votes
1 answer
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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 $$\...
user213305's user avatar
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1 vote
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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 ...
aerospace's user avatar
3 votes
1 answer
415 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 ...
aerospace's user avatar
4 votes
1 answer
1k 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) ...
Pavithra J's user avatar
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 ...
Wychh's user avatar
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6 votes
1 answer
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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 ...
C. Alexander's user avatar
9 votes
0 answers
378 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 ...
C. Alexander's user avatar
6 votes
1 answer
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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 ...
Pablor's user avatar
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2 answers
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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 ...
pH13 - Yet another Philipp's user avatar
7 votes
1 answer
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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 ...
user2872903's user avatar
25 votes
0 answers
2k views

How to calculate transition dipole moment from two known wavefunctions

I am 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 ...
brose's user avatar
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10 votes
2 answers
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How to interpret orbital transition in TDDFT?

Consider the following TDDFT run with GAMESS: ...
Aug's user avatar
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3 votes
1 answer
871 views

How to interpret TD-DFT results for finding λmax and amplitude

I am trying to understand how to interpret the TDDFT results ( I know there is another post for this but it does not answer my question ). Here is part of the result from GAMESS: I downloaded ...
Aug's user avatar
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3 votes
1 answer
2k views

Which is most reliable excitation energy: LUMO-HOMO energy or TD-DFT excitation energies?

After running a TD-DFT , we can calculate the HOMO-LUMO difference and then calculate the the excitation energy. Another approach is just simply pick the energies calculated in the TD-DFT and use ...
Aug's user avatar
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18 votes
1 answer
7k views

Interpretation of TD-DFT results

For the first time I'm doing TD-DFT calculations (wB97XD functional) in Gaussian 09 for an open-shell system and the results look like the hell of a mess for me. The molecule is rather big, so I ...
Wildcat's user avatar
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4 votes
0 answers
798 views

How to Locate the Excited State Dipole Moment in Turbomole Output (TD-DFT)

I want to calculate the dipole moment for the first excited state with a Q.C. program (TURBOMOLE: TD-DFT). The calculation lists the following output: ground state total dipole moment: ...
tmartin's user avatar
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