16 votes

How to understand the spin of exciton?

As you mentioned in the question, excitons are indeed bound electron-hole pairs. They are often considered to be the signature of optical spectra in insulating solids. Adding onto the comment by tmph, ...
Xivi76's user avatar
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14 votes
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What methods can be used to calculate excited-states in molecular crystals?

There's two facets to this question: What methods can be used for excited states in crystals? (the title, and final sentence) What methods can be used for excited states with plane waves? (paragraphs ...
Nike Dattani's user avatar
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13 votes
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What methods are available for excited state calculations in solids?

$\Delta$SCF This method generates excited states by changing the occupancy of a ground state determinant and then carrying out a new SCF with that initial guess, with some restriction throughout to ...
Tyberius's user avatar
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11 votes

Can you estimate the electronic excited state lifetime of a molecule?

The Einstein A coefficient (as mentioned in Cody's answer) tells you the probability per unit time of spontaneous radiative decay from an excited state to a lower state. The Fermi golden rule (as ...
Nike Dattani's user avatar
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10 votes
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Can you estimate the electronic excited state lifetime of a molecule?

tldr; it's related to the excitation energy The lifetime of an excited molecule assuming there are no non-radiative pathways, is related to the Einstein A coefficient: $\left(\frac{dn_2}{dt}\right)_\...
Cody Aldaz's user avatar
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10 votes

What methods are available for excited state calculations in solids?

GW+BSE: Excited states in the framework of many-body Green's function comprise charged excitations, where the number of electrons in the system changes from $N$ to $N-1$ or $N + 1$, and natural ...
Jack's user avatar
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9 votes

How to understand the spin of exciton?

First I mention this very similar question on Physics SE and the related answer. Then, a couple of points which are not well addressed in the previous answer in my opinion. First of all we are here ...
Davide Sangalli's user avatar
9 votes

Is it reasonable to calculate TDDFT excitation energies at a geometry optimized with a different method?

From my point of view, it will not affect so much on the excitation energy, but it is preferred to use the same level of functional and basis set unless you will increase the level of theory to get ...
Abd-Elazeem Mohamed's user avatar
8 votes

Can you estimate the electronic excited state lifetime of a molecule?

Fermi golden rule should give you the transition probability (per time), from which you should be able to estimate the lifetime. You should know of be able to estimate the density of states in the ...
sleepy's user avatar
  • 291
8 votes

What are the recent developments of GW@BSE to simulate the excited properties of materials?

As one of the members of the Yambo group I can answer for the developments, in the Yambo code, in particular related to GW and BSE. One important aspect is the code optimization, and the connected ...
Davide Sangalli's user avatar
7 votes
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Is there an example where TD-DFT fails to provide sufficient accuracy for a small system, where RI-CC2 is sufficient?

The question cites a 2008 paper about fairly large molecules (e.g. bithiophene N-succinimidyl esters), in which TD-DFT gave significantly wrong results, so the authors recommended RI-CC2. The question ...
Nike Dattani's user avatar
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7 votes
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Calculating the excited state dipole moment

This looks like it has been addressed on the CCL previously. To summarize and add details for your case, Gaussian can directly calculate the excited state dipole, but you need to add the keyword ...
Tyberius's user avatar
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7 votes

Calculating the excited state dipole moment

There's actually more than one way to calculate the dipole moment, and you can check whether or not the numbers you're obtaining from td=(singlets,nstates=5,root=1) ...
Nike Dattani's user avatar
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7 votes
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How can I calculate the energy gap between the singlet and triplet state using ORCA?

First of all, if you are only interested in molecules with about the same size as the ones in the article you cited, then TDDFT is probably not the best method for this purpose. ORCA supports many ...
wzkchem5's user avatar
  • 9,366
7 votes

Any software that could do surface hopping?

Here are some options. Depending on what you want you may use on-the-fly electronic structure calculations for energies, gradients, and couplings and some of the codes can take care of integrating the ...
Antonio de Oliveira-Filho's user avatar
7 votes
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Is it reasonable to calculate TDDFT excitation energies at a geometry optimized with a different method?

The question, in some sense, is "how accurate is the geometry?" Yes, in principal, you should do TD-DFT on a true minimum geometry. However, the diagram also indicates that if you displace ...
Geoff Hutchison's user avatar
7 votes

Vertical transition, 0-0 transition, and experimental spectra

Yes, the absorption maximum is usually close to (but not necessarily exactly equal to) the vertical excitation from the ground state, due to the Franck-Condon principle. However, this does not mean ...
wzkchem5's user avatar
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7 votes
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S1-T1 energy difference in Gaussian

The excitation energies are 3.09 and 2.17 eV, respectively, both relative to the (same) ground state, and thus the energy difference is 3.09 - 2.17 = 0.92 eV. The Total Energy is the ground state ...
Frank Jensen's user avatar
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6 votes

Any software that could do surface hopping?

Newton-X Newton-X is a general program for molecular dynamics simulations beyond the Born-Oppenheimer approximation. It has been primarily used for simulations of ultrafast processes (femtosecond to ...
Felix's user avatar
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6 votes
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Optimization and vibrational analysis of excited state CO using GAMESS

I cannot see your output file, but I am pretty sure that the program is running into an error when starting the optimization i.e. when it is trying to generate the guess hessian. You are using ...
S R Maiti's user avatar
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6 votes

Closed-form expression for excitation energies, given the exact XC functional

No, they cannot be obtained from a DFT calculation. As the first paper I linked in the previous response says, DFT is a ground state theory, and it should not be expected to get excited state ...
AGS's user avatar
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6 votes
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Optimise S1 geometry with CASSCF in ORCA

I see two possibilities here: you adjust the weights of the roots such that the weight of the s0 root is 0.0 and the weight of the s1 root is 1.0. then you have to hope for the best that the s1 state ...
FrankNeese's user avatar
5 votes
Accepted

Excited state normal mode frequency doesn't match for NH3

This is not a full answer, because it does not solve the problem. But I hope to shed some light on why you are not getting the correct frequencies. Short answer: I suspect there is a bug in GAMESS ...
S R Maiti's user avatar
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5 votes

Excited state normal mode frequency doesn't match for NH3

I can see two major problems: CCD != CC2 and I'm not certain if CC2 is available in GAMESS. CC2 is an approximation of CCSD, which is available in GAMESS. You may be able to use this since $\ce{NH3}$ ...
Tyberius's user avatar
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5 votes

What are the recent developments of TDDFT to simulate the excited properties of materials?

Time-dependent density functional theory (TDDFT) has indeed seen significant developments since its review in the classical paper you mentioned. One of the recent advancements in TDDFT is: Nonlinear ...
Jaafar Mehrez's user avatar
5 votes
Accepted

Photoemission Spectra of Solids

This is a complicated question for which I do not have a full answer. However, here are some thoughts: Excited state relaxation. In solids, the calculation of excited states typically requires the ...
ProfM's user avatar
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5 votes
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Question on generalised Kohn-Sham "band gap"

The optical band gap is not expected to equal the DFT band gap since excitonic effects are not included. What you are referring to is the fundamental gap. The fundamental gap is related to electron ...
AGS's user avatar
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5 votes
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Closed-form expression for excitation energies, given the exact XC functional

Do you consider the exact frequency-dependent XC kernel as part of "the exact XC functional"? And do you allow the use of additional ingredients like two-electron integrals? If both of your ...
wzkchem5's user avatar
  • 9,366
5 votes
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Quantum Chemistry software that can calculate nonadiabatic coupling vectors between excited states using DFT/TDDFT

The BDF program (https://bdf-manual.readthedocs.io/en/latest/; the English manual is under ongoing translation from Chinese. For a purely English but older version, see http://182.92.69.169:7226/...
wzkchem5's user avatar
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5 votes
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Does it make any sense to run a TD-DFT calculation with Finite-Temperature SCF active?

Temperature affects a system through two ways: (1) by (loosely speaking) making the nuclei move faster, and (2) by exciting some electrons to virtual orbitals (or equivalently speaking, exciting some ...
wzkchem5's user avatar
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