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, ...
- 2,332
12
votes
How many spin states do Cu+ and Cu2+ have and why?
$\ce{Cu}^+$
This ion has 28 electrons. If all of them are up (i.e. aligned with the +z axis), then since each electron has a spin of magnitude 1/2, we would have a total spin of +14. If all of them ...
- 33.6k
11
votes
How many spin states do Cu+ and Cu2+ have and why?
Often when one is asked for the number of spin states, we are interested in determining the spin state of metal complexes containing these ions, rather than the lone ion itself. If you are interested ...
- 15.2k
10
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Spin State of Transition Metal complex
For computing the spin-state in a metal complex there are many methods available. I'll focus in DFT as one of the most used methodologies.
In a single atom cluster (sometimes described as mononuclear ...
- 1,590
10
votes
When should spin polarized calculations be done?
Unfortunately, without performing spin polarized calculations you cannot know if it will matter. Further, you must perform different magnetic configurations (AFM, FM, PM) to know which is stable.
...
- 10.8k
9
votes
Accepted
When should spin polarized calculations be done?
I agree with Tristan that the fool proof method is to do a spin-polarized self consistent calculation and look at the final magnetic moment. If the final magnetic moment is non-zero you should include ...
- 8,922
9
votes
How to automatically plot atomic structures with magnetic moments?
This took some digging, but I can supply at least a partial answer.
Assuming you can copy the list of magnetic moments to a list, you could trick whatever software you are using for visualization into ...
- 10.8k
9
votes
Accepted
Why can't we change the spin angular momentum of electrons with an external optical field?
This has already been asked in several forms in Physics Stack Exchange. Within the semi-classical 'electric dipole' approximation, only the electric field of light interacts with the electron. The ...
- 2,332
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 ...
- 466
8
votes
What do we mean by spin-splitting energy?
The word "splitting" seems to occur only in one sentence, over the course of the entire paper that you referenced:
"The d-orbital spin-splitting energy is stronger than the weak ...
- 33.6k
8
votes
Accepted
How to find out the multiplicities of molecules containing d and f block species?
With metals, they can often exist as different multiplicities depending on the compound they are in and it is not always simple to predict the correct multiplicity. More often than not, determining ...
- 15.2k
8
votes
Accepted
What are alpha and beta electrons?
Alpha and beta basically denote spin-up (+1/2 for electrons) and spin-down (-1/2 for electrons).
This tells us how the spin would align if we have a magnetic field. A spin of +1/2 actually means that ...
- 33.6k
6
votes
Accepted
How to detect an "open shell" molecule?
When you're doing an electronic structure calculation, the input will include the following things:
Geometry
Basis set
Number of electrons
Spin multiplicity
If the spin multiplicity is not 1 (i.e. ...
- 33.6k
6
votes
Accepted
Spin considerations for the bandgap and optical excitations
I don't think we need to talk about driving forces (this sounds esoteric) instead calculating the selection rule:
$$P_T = \int \psi_1^* \mu \psi_2 d\tau$$
Here $\psi_1$ and $\psi_2$ are the ...
- 22.3k
6
votes
Why can't we change the spin angular momentum of electrons with an external optical field?
well, you certainly can change the spin of an electron through acting on its orbital motion with the electric field. It is called "spin-orbit coupling" (SOC) and a lot of magneto-optical and ...
- 291
5
votes
5
votes
Accepted
How to interpret spin density isosurface figures?
How to interpret this figure below? And what is the meaning of the blue and yellow color around atoms?
This figure basically tells you the probability that you can find spin-up and spin-down ...
- 14.9k
5
votes
Why can't we change the spin angular momentum of electrons with an external optical field?
I think the claim assumes linear polarization of the light which has zero angular momentum. For circularly polarized light, the spin of the electron should be flipped. (e.g. Appl. Phys. Lett. 114, ...
- 2,048
5
votes
Accepted
What do we mean by spin-splitting energy?
I see now how your initial questions were related, as they all fall under the scope of crystal field theory. I wrote a bit about this in a previous answer.
At least in the context of molecular crystal ...
- 15.2k
5
votes
How to find out the multiplicities of molecules containing d and f block species?
To obtain the spin multiplicity of the ground electronic state of a molecule, can be extremely hard.
In your question you mentioned $\ce{UF6}$ which has 7 atoms, and not all of them being of the same ...
- 33.6k
4
votes
How to select charge and multiplicity for macro-molecules?
Unless there are transition metals (e.g. Fe, Mn, Cu, Ni) present in the active site, proteins typically have singlet state. There are several programs out there, such as propka, that can propose ...
- 1,034
4
votes
How to select charge and multiplicity for macro-molecules?
Sometimes the protein has been studied experimentally (or thoroughly by theory), and a consensus has been made about the most common charge and multiplicity for the molecule. In most cases, I would ...
- 33.6k
4
votes
Accepted
What are the precise forms for the SU(2) and rotation matrices in VASP?
The answer you got on the VASP forum here (thank you for giving us that in your question!) said to look in spinsym.F but was not clear at all, especially due to the ...
- 33.6k
4
votes
Spin considerations for the bandgap and optical excitations
What are the consequences for a bandgap if the conduction band and valence band are on different spins?
The energy band of materials when the spin is involved (magnetic/nonmagnetic) are usually ...
- 14.9k
3
votes
Accepted
How to predict spin liquid materials with DFT?
I suspect this would be very difficult to do with DFT. A spin liquid is a very subtle magnetic state and DFT, as a method, is not usually good at describing the magnetic states of a system. Spin ...
- 6,579
3
votes
Accepted
Can crystal field splitting energy or spin-splitting energy be detected in a density-of-states plot? How?
I'm going to reproduce the part of my answer from the linked question that relates to the spin-splitting.
I don't believe the spin-splitting or field splitting can be read from the DOS. The way they ...
2
votes
How to compute spin projections in QE?
If you do a noncollinear calculation, you can then get the spin projections along the x, y and z axes by utilizing the post-processing executable pp.x and choosing <...
- 608
2
votes
Density functional theory and oxygen spin
I don't have much experience with QE, but in VASP, which I imagine is pretty similar, oftentimes not setting an initial magnetization on each ion results in zero magnetic moments on those ions. This ...
- 106
2
votes
Table of Largest CI Components in PySCF CASSCF Calculation
You have 4 electrons in 4 spatial orbitals. Number the orbitals 0, 1, 2, and 3.
Look at the lowest root. It is an open shell singlet. The spatial orbital 0 is doubly occupied, and then you have (12-21)...
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