Total magnetization of an isolated atom

In summary, an isolated atom of Boron has a magnetic moment that is composed of the spin and orbital moments. The total magnetic moment is determined by the level of fill in the shells, and the molecule with only 8 magnetic Iron atoms is complicated enough to be studied in detail.f
  • #1
im trying to study an isolated atom(Boron) and i can't for the life of me figure out what to do with the total magnetisation, which is defined as :
quantum_espresso said:
total majority spin charge - minority spin charge.
further more:
quantum_espresso said:
Used to impose a specific total electronic magnetization.
what are these guys talking about? is this explained out in detail somewhere in ENGLISH for humans?
  • #2
I've been researching boron for over 30 years, and _might_ have learned something in the process, presuming of course that what you 'think' you know about boron will prove to be incomplete or flat out wrong the longer you study it. I just stumbled into this forum and your post, so I've missed the rest of the thread and have no context for understanding what your specific interest in boron actually is. Care to fill me in?

Forums are something new to me, and I'm not sure how to plug in again for your answer or navigate the forum very well yet. You can also get in touch with me by using my log-in name 'at' mac dot com.
  • #3
To understand the magnetic moment of isolated atoms, take a look at Hund's rules. There are plenty of good explanations around in nearly every language spoken on this planet.

Unlike boron fibers, a single, isolated, neutral atom of boron is something we can still handle.

If you look at Webelements, for example, you will find the electronic configuration of Boron given as

[He] 2s^2 2p^1

this means that you have all levels filled up to the Helium configuration [He], and then you add 2 electrons to the 2s-shell and one to the 2p shell.

A completely filled shell has no magnetic moment.
The s-shell can hold 2 electrons,
The p-shell can hold 6 electrons,
The d-shell can hold 10 electrons...

[He]=1s^2 completely filled=no magnetism.
2s^2 completely filled=no magnetism.
2p^1: particlely filled=magnetic moment. In this case one single, unpaired electron.

According to Hund's rules this gives the magnetic state S=1/2, L=1, J=L-S=1/2

The total magnetic moment (J) is composed of the spin (S) and orbital moments (L).

When you put several atoms together, things get very complicated very quickly. Unpaired electrons start to form bonds, orbital moments can become quenched, and whatever magnetic moments remain on the atoms or ions start to interact. A molecule with only 8 magnetic Iron atoms (and some vegetables around them, to make it look nice), for example, is complicated enough to be subject of ongoing research.

Welcome the the wonderful world of quantum mechanics.
  • #4
That's wonderful information, thank you very much. The veggies are a nice touch, any recommendations ? My daughter tells me I need to incorporate more of them in my diet.

I'm trying to educate myself in QM because I'm discovering that it is the only approach to boron that makes sense. I've been banging my head for years trying to reconcile boron with Classical Physics, but CP eventually concludes that it shouldn't even exist in the first place.

I'm an experimentalist, and have been researching solid-state boron cluster chemical-physics for decades and occasionally questioned my sanity because boron's so weird.

I have to start with inexplicable experimental artifacts, and then try to deduce the physics by deconstructing the tangible experimental phenomena common to things which shouldn't be happening at all.

Are you familiar with 'quantum electron hopping' between the two outer shells? A boron atom is truly schizophrenic because its valence is constantly changing as the electron 'hops' back and forth between the shells in a quantumish sort of way.

It's natural configuration is icosahedral, which gets to be really messy if each atom has the freedom to randomly flip valences. My head hurts every time I try to visualize the idea. Just to make things even more fun, it has two stable isotopes 20%$ 10B and 80% 11B, so in any given 12-atom icosahedron that stoichiometry becomes a game of statistical probability as well. Somehow the icosahedra have to work out an asymmetric packing density arrangement, and somewhere I stumbled on to a graphic with the title 'Icosahedron Charge Density', which claimed that "bonding does not happen at the vertices of the structure like one would imagine, but across the faces of it" Just found the source > <.

What do you do with boron ?

  • #5
Nothing really. but the question was about boron, and that is as easy to look up as any other atom.

I am an experimentalist, however, and have done a bit of work with x-rays and on magnetism.

What you say about boron makes my head spin. As soon as you start talking about bonds, hopping and mixed valence you HAVE to use QM. There is no way around it. But when you look at the electronic properties, the difference between 11B and 10B should not matter so much. BTW, I vaguely recall that icosahedra form the basis of quasicrystals, but are "forbidden" in ordinary crystals?!?


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