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18 votes

How to incorporate the effect of spin-orbit coupling in electronic structure calculation

The inclusion of spin-orbit coupling in electronic structure calculations is done by including the interaction between the electron-spin and the orbital angular momentum in the Hamiltonian. Such ...
Meilani Wibowo's user avatar
16 votes
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How to incorporate the effect of spin-orbit coupling in electronic structure calculation

Basically there are two kinds of approaches which may be found in many text books, L-S coupling and j-j coupling. L-S coupling means that scalar electronic states (e.g. atomic L-S states and linear ...
Zork's user avatar
  • 176
15 votes
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When do relativistic effects need to be explicitly included?

When to include relativistic corrections or modeling of any kind in computational methods is a rather complex one. Full Dirac methods as you asked about (DHF) recapture two important factors, so ...
Raz Jugovic's user avatar
15 votes
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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 ...
Xivi76's user avatar
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12 votes
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Why were no correlation consistent basis sets for potassium contracted for a non-relativistic Hamiltonian?

The answer in part is that not all the elements up through $\ce{Xe}$ have (or had until fairly recently) a nonrelativistic correlation consistent basis set. Specifically, the alkali and alkaline earth ...
Tyberius's user avatar
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10 votes
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Software for quantum electrodynamics?

GRASP Allow me to introduce you to GRASP, a software that was written largely by now 92-year-old Ian Grant and now 94-year old (5 days from now) Charlotte Froese Fischer whose PhD supervisor was ...
Nike Dattani - No Free Time's user avatar
10 votes

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 ...
Nike Dattani - No Free Time's user avatar
9 votes
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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 ...
Jack's user avatar
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9 votes
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Theoretical origins of stereochemistry

Relating to the question about electroweak chemistry: the parity violation effect of the weak force on chiral asymmetry has been considered for quite a while now. A good accessible introduction to the ...
Emil Zak's user avatar
  • 896
9 votes

When should I include semi-core electrons in DFT calculations?

I am quoting from the book Materials Modelling Using Density Functional Theory: Properties and Predictions by Feliciano Giustino How do we decide which wavefunctions should be considered ‘core’ and ...
Thomas's user avatar
  • 9,162
9 votes

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 ...
wzkchem5's user avatar
  • 9,710
8 votes
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Acceleration of 8110823001207866000 m/s^2 by using Coulomb's law: did I do it right?

The other answer correctly pointed out that using $F=ma$ and the mass of the hydrogen atom does not give the exact $a$, and even if one uses the correct relativistic formulas and the correct mass, one ...
wzkchem5's user avatar
  • 9,710
7 votes

Acceleration of 8110823001207866000 m/s^2 by using Coulomb's law: did I do it right?

"It rises the question, if Columb's law can be useful at such small/atomic scales?" Coulomb's law still plays a role in the Hamiltonian of an atom, but your discussion of "force" ...
Nike Dattani - No Free Time's user avatar
7 votes

Quantifying relativistic effects in DFT calculations

In reality, the contribution to an energy due to relativity, would be the difference between the "exact" energy with a model that captures all relativistic effects, versus a model that ...
Nike Dattani - No Free Time's user avatar
7 votes
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Calculating Te chemical shifts with Gaussian

def2-TZVP employs an effective core potential on Te, which describes the innermost 28 electrons only implicitly; this is almost certainly the cause of the problem. I am surprised the program even ...
Susi Lehtola's user avatar
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6 votes
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On mass polarization terms

You may find derivation of eqs.120-124 in these notes Normal modes. The true story. helpful in revising your derivation. Answering the other question: centre-of-mass can always be separated by the ...
Emil Zak's user avatar
  • 896
6 votes
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What is the meaning of energy-consistent and shape-consistent in the context of pseudopotentials?

This 2017 paper titled "Shape and Energy Consistent Pseudopotentials for Correlated Electron systems" defines energy-consistent psuedopotentials this way: "A combined reproduction of ...
Nike Dattani - No Free Time's user avatar
6 votes

What are some of the advantages and disadvantages when using shape consistent pseudopotentials as compared to energy consistent pseduopotentials

The advantages and disadvantages are discussed in this review paper which was cited in Susi Lehtola's answer to: What are the types of pseudopotentials? and then again in my answr to: What is the ...
Nike Dattani - No Free Time's user avatar
5 votes

Scalar relativistic Calculation for pseudopotential

There is no scalar-relativistic effect. "Scalar-relativistic" is an approximation to the fully relativistic treatment. The main simplification in this technique is the neglection of spin-...
Gregor Michalicek's user avatar
5 votes
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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, ...
Xivi76's user avatar
  • 2,402
5 votes

What are some of the advantages and disadvantages when using shape consistent pseudopotentials as compared to energy consistent pseduopotentials

Shape consistent pseudopotentials are just commonly used for some reason, even though energy consistent pseudopotentials are "the right way to do it". The reason why shape consistent ...
Susi Lehtola's user avatar
  • 19.8k
5 votes

When should I include semi-core electrons in DFT calculations?

Many DFT codes use pseudopotentials (for the core electrons) and basis set functions (for the valence electrons) in order to solve the Schrodinger equation. This because simulates each electron ...
Jack's user avatar
  • 15.2k
5 votes

Why were no correlation consistent basis sets for potassium contracted for a non-relativistic Hamiltonian?

Like many others, the correlation consistent sets start from an MCHF (i.e. small CASSCF) ground state calculation. For Li and Be the MCHF ground state has S orbitals only, but there's also a low lying ...
Susi Lehtola's user avatar
  • 19.8k
5 votes

How to incorporate the effect of spin-orbit coupling in electronic structure calculation

Spin-orbit coupling effect can be included in electronic structure calculations using variational methods such as fully relativistic four-component Dirac HF or KS approach, or two-component approaches ...
QMlab's user avatar
  • 976
4 votes

When should I include semi-core electrons in DFT calculations?

You are making an approximation by including the semicore states in the pseudopotential. Like the name suggests, semicore states aren't really core states; they lie higher up in energy so they may not ...
Susi Lehtola's user avatar
  • 19.8k
4 votes
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What is the difference, if any, between an effective core potential (ECP) and a pseudopotential?

They are often used as synonyms Schwerdtfeger's review paper "The Pseudopotential Approximation in Electronic Structure Theory" states that the two terms are used as synonyms in the ...
Nike Dattani - No Free Time's user avatar
3 votes

How do scalar states with different multiplities make spin-forbidden reactions possible?

No, the presence of scalar states with different multiplicities is only a necessary condition for spin-forbidden reaction to take place (because otherwise there are no spin-forbidden reactions), but ...
wzkchem5's user avatar
  • 9,710
3 votes

How to generate relativistic pseudo-potential using Vanderbilt USPP that captures spin-orbit coupling?

The spin-orbit effect is something that your code has to be able to do, it is not a property of the pseudopotential. Here you can find other discussions about it: How to incorporate the effect of ...
Camps's user avatar
  • 23.7k
2 votes

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

The spin-orbit coupling is an interested phenomena very present in semiconductor physics (no heavy atoms here). It affects the behavior of electrons and is a very important property explored in the ...
Camps's user avatar
  • 23.7k
2 votes

Converging the potential of a dilute binary alloy system using the Coherent Potential Approximation. What troubleshooting options could I take?

I managed to get the converged U$_{0.01}$Cu$_{0.99}$ potential by converging a pure Uranium potential in a Cu lattice. Then by increasing the concentration of Cu and using the old converged potential ...
LUPHYS's user avatar
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