An effective, but not actual, force used for effective description of geometric effects between identical particles, such as the apparent repulsion between fermions due to the Pauli principle.
Questions tagged [exchange-interaction]
80 questions
25
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Simple description of exchange interaction?
What is a simple bare-bones description of exchange interaction between two electrons?
For instance, it seems to me that the only necessary ingredients are the Coulomb interaction and the requirement that the total wavefunction be antisymmetric.
BeauGeste
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2 answers
Are all electrons identical?
Why should two sub-atomic (or elementary particle) - say electrons need to have identical static properties - identical mass, identical charge? Why can't they differ between each other by a very slight degree? Is there a theory which proves…
Gsv
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Which mechanism causes ferromagnetism in iron?
There are at least three different mechanisms which can give rise to ferromagnetic order in iron.
First is due to the band electrons called band magnetism or itinerant magnetism which is an exchange interaction between conduction electrons.
The…
Solidification
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11
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3 answers
Why don't all elements with unpaired electrons become ferromagnetic?
As a necessary condition, ferromagnetism in elements requires the existence of unpaired electrons. However, all elements with unpaired electrons are not ferromagnetic, e.g., metals such as aluminium or copper are either paramagnetic or diamagnetic.…
Solidification
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10
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2 answers
What is the “exchange energy of electrons”?
First, do not try to give me the perplexing explanations involving higher QM. I am new to QM, so please give a gentle explanation.
Now, my textbook see page 36 states that electrons of degenerate orbitals of same subshell and with same spin, tend to…
user95732
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8
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DFT: When would one use a LDA over a GGA method?
Computationally using Density Functional Theory (DFT), is there any examples where Local Density Approximation (LDA) would be preferred over using Gradient Generalized Approximation (GGA) methods for the exchange-correlation term of the Kohn-Sham…
furg berful
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6
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2 answers
How can the exchange interaction make electron spins parallel?
Electrons repel by Coulomb interaction. When they get too close, Pauli exclusion principle ("Exchange interaction") becomes important. If their spins are parallel, they are further "pseudo-repelled". If they are anti-parallel they are…
Juan Perez
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Are combined fermion wavefunctions still antisymmetric after wavefunction collapse?
If we have two electrons in a state $|\psi\rangle=\frac{1}{\sqrt2}[|\uparrow\downarrow\rangle+|\downarrow\uparrow\rangle]$ and we measure the spin of the first electron to be up, does the wavefunction collapse into the state…
Alex Gower
- 2,684
6
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1 answer
Does the (non-)collision of two fermion wave packets demonstrate that there is no exchange "force"?
In the paper "Quantum statistics: Is there an effective fermion repulsion or boson attraction?" by Mulling and Blaylock (2003), it is claimed that
We can demonstrate there is no real force due to Fermi/
Bose symmetries by examining a…
Codename 47
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Different types of magnetic exchange
I am a bit confused about the mechanisms of different types of exchange. Mainly, I am trying to understand mechanisms that lead to magnetic ordering and I came across several different types of exchange:
Direct exchange
Double…
Xivi76
- 153
5
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1 answer
How would Kohn-Sham orbitals differ from 'true' elecron wavefunctions?
How would the non-interacting electron orbitals from a perfect DFT solution for a given potential shape differ from the 'true' electron wavefunctions? Or can you only really talk about the total wavefunction? Would they be less localised as they do…
Phil H
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Why does exchange lower energy with increasing electron density in Hartree-Fock
The Hartree-Fock equations include a term for the exchange interaction, which is usually explained as a repulsive force due to the Pauli exclusion principle. (It says so right in the description for the "exchange-interaction" tag.)
I expect that, in…
lnmaurer
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4
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2 answers
Example of a wavefunction that cannot be represented by a single Slater determinant
I know that in general, interacting fermions cannot necessarily be described by a single Slater determinant. Can anyone provide a simple example of a state that has no such representation?
Dan
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How do spins interact with each other?
When talking about magnetism and the interaction of spins, the most basic model seems to be the Heisenberg model with an interaction of the form $ -J \vec{S}_1\cdot \vec{S}_2$. The origin of the contribution seems to be coming from the exchange…
Stephphen
- 187
3
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2 answers
Why classical mechanics is not able to explain the net magnetization in ferromagnets?
Why classical mechanics is not able to explain the net magnetization in ferromagnets?
why does exchange interaction can explain net magnetization in Ferromagnets, which is purely quantum mechanics??
