# Tag Info

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### Total spin and/or multiplicity for transition metal ions?

Even for the simplest transition metal diatomic molecules, the most reliable way to know the ground-state spin configuration is often by doing experiments. I will give an example where it's easy to ...
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### What's the difference between spin-unpolarized, spin-polarized and non-colinear calculation?

Noncollinear magnetism means that the orientation of the magnetization varies in space. Examples for such structures are magnetic domain walls, spin spirals, or magnetic skyrmions. To describe these ...
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### Spin–orbit interaction with DFT

There are options to include spin-orbit coupling in DFT. In general, there are two ways to do it: Solve Dirac's relativistic equation for the electrons Incorporate relativistic effects through the ...

### What is the difference between Ultrasoft, ONCV and PAW Pseudopotentials? Which is better for a spin-orbit coupled calculation?

Pseudopotentials (PPs) describe the effective interaction between the valence electrons and a nuclei screened by frozen core electrons. This approximation makes DFT calculations less computationally ...

### 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 ...
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### How to determine which levels correspond to each other in LS coupling and jj-coupling?

In the jj-representation, each electron from $i$ to $N$ will have: $\vec{l}_i$ (orbital angular momentum), $\vec{s}_i$ (spin angular momentum), and $\vec{j}_i=\vec{l}_i + \vec{s}_i$ (total angular ...

### 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 ...

### What's the difference between spin-unpolarized, spin-polarized and non-colinear calculation?

Basically, this is the split between restricted, unrestricted, and generalized Hartree-Fock (or Kohn-Sham) theory. In the restricted theory, both the spin-up and spin-down electrons occupy the same ...
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### Error in nscf calculation while considering Spin Orbit Coupling in Quantum ESPRESSO

This error has been resolved now. Though I am not an expert but here are few thoughts. There may be several reasons for this error: This error might appear due to numerical instability from ...

### Total spin and/or multiplicity for transition metal ions?

If you're studying transition metal complexes, in short, there is no simple way to know except for to try the relevant physically plausible spin multiplicities and take the lowest energy solution as ...

### For which elements should I include spin orbit coupling in Quantum ESPRESSO?

Spin-orbit coupling is related to relativity which is increasingly important for heavier elements. If you're aiming for ultra-high precision, as in this post on our site: How accurate are the most ...
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### SOC calculations in VASP

Sometimes the forces will be similar with and without SOC, so you can relax without SOC, and then do a single point calculation on the relaxed structure with SOC. When you do that calculation, you ...

### How spin-orbit coupling makes spin-forbidden reactions possible?

TL;DR: The statement $[H,S^2]=0$ indeed holds for no-pair (i.e. without considering the production of electron-positron pairs) calculations of hydrogen-like ions, but not for general atoms and ...
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### For which elements should I include spin orbit coupling in Quantum ESPRESSO?

But in the case of the pseudo-potentials included, should I use fully relativistic pseudopotentials for all three elements? Yes, you should use the fully relativistic pseudopotentials if you are ...

### Should I use a lower threshold for calculations involving SOC?

I wouldn't recommend that you go above $10^{-8}$, what you have in your current calculation. With SCF calculations, you definitely need a lower convergence threshold compared to say relaxing ...

### Spin orbit coupling from spin polarized density of states?

I'll try to be as basic as I can in regard to explaining the stuff youve posted. From what I read online, spin-orbit coupling is how the angular momentum of an electron w.r.t. the nucleus interacts ...

### What's the difference between spin-unpolarized, spin-polarized and non-colinear calculation?

As far I understand, to search for spin-polarized solutions, the DFT code will have to solve two coupled Kohn-Sham equations, one for each of the two spin species. There is both direct and indirect ...

### How to obtain spin projected band structure for system with Spin Orbit Coupling?

Phil's answer is absolutely correct. In non-collinear spinor calculation The spin for each state (at a specific k-point and specific band) can points towards different direction. However, since spin ...

### How to obtain spin projected band structure for system with Spin Orbit Coupling?

Non-collinear spin doesn't mean there's no "up" and "down", it means that the natural quantisation axis (which defines "up" and "down") can vary in space. In ...

### Spin density in systems with non-collinear magnetism using VASP

Extracting the spin density should supposedly be as simple as reading the CHGCAR and extracting the X Y Z density separately (It is all output). You can then treat this the same way as spin up / down....
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### In which cases should SOC be included?

Spin-orbit coupling scales as $Z^4/n^3$ where $Z$ is the atomic number and $n$ is the principal quantum number. When you move down the periodic table and the nucleus becomes heavier and heavier, ...

### HSE06+SOC method using VASP

A complete input card is given for the previous post about HSE06+SOC band structure calculation. Step-I: DFT SCF calculation with SOC (INCAR): ...

### Spin-Orbit coupling effects in topological insulator Bi2Se3

Welcome to MMSE! That's an interesting question! At first the "crossing" of energy levels seemed peculiar to me, but when I look at the energy levels for Se and for Bi separately, everything ...

### How to change the spin-orbit coupling strength in VASP?

How to change the spin-orbit coupling strength in VASP? Firstly, one can't realize this just by changing the input parameters in the INCAR for ...
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### How to formulate the second quantization of Dzyaloshinskii-Moriya interaction?

Let's first break down the symbols we know in that expression: \begin{align} \mathbf{\vec{S}} &= \frac{\hbar}{2}\boldsymbol{\vec{\sigma}}\tag{1}\\ &=\frac{\hbar}{2}\left(\sigma_x \boldsymbol{\...
What is spin-orbit coupling (soc) and what does soc strength mean? The spin-orbital coupling (SOC) is a relativistic effect. Mathematically, it can be represented as: $$\vec{L} \cdot \vec{S}$$ in ...