Live data from Hacker News

Electron band structure in germanium, my ass (2000)

pages.cs.wisc.edu

11–20 of 88 posts

Re: Electron band structure in germanium, my ass (2000)

#12

Not really related of the article, but a question I just realized I don’t know the answer to: where does the temperature of an atom “live”? Is it entirely in the electrons? Does the nucleus have any temperature?

https://physics.stackexchange.com/q/716282/43345 discovered by me some time ago. Long story short, nucleus cannot absorb low temperature thermal energy so it's virtually zero.

Re: Electron band structure in germanium, my ass (2000)

#13

Not really related of the article, but a question I just realized I don’t know the answer to: where does the temperature of an atom “live”? Is it entirely in the electrons? Does the nucleus have any temperature?

The "temperature of an atom" is something very different from the temperature of a material with billions of atoms. For the material, what matters most is usually vibrations of atoms, where the nucleus contributes the most to kinetic energy, because it is heavy, and the electronic configuration contributes to potential energy.

For an atom, you basically have to do quantum physics and talk about von Neuman entropy of it's quantum state. This kind of temperature is very removed from the everyday concepts of "heat" and "heat transfer".

Re: Electron band structure in germanium, my ass (2000)

#14

Not really related of the article, but a question I just realized I don’t know the answer to: where does the temperature of an atom “live”? Is it entirely in the electrons? Does the nucleus have any temperature?

Temperature is the motion of the whole atom. Individual atoms don't really have temperature, temperature is a bulk property, the average of motion of lots of atoms.

Re: Electron band structure in germanium, my ass (2000)

#15

Not really related of the article, but a question I just realized I don’t know the answer to: where does the temperature of an atom “live”? Is it entirely in the electrons? Does the nucleus have any temperature?

That's a good question. it depends how long you wait and how strongly coupled they are.

For electrons and nuclear motion they are often strongly coupled enough that they quickly reach equilibrium and thus are at the same temperature (e.g. in liquids or solids). But on short timescales they can absolutely be at distinct temperatures. In dilute gases they can also become somewhat decoupled (there can be a well defined electronic temperature and nuclear temperature).

One case whether this can take a much longer period of time is when dealing with nuclear spin -- this is much more weakly coupled to the electrons and so can take much longer to equilibriate.

Re: Electron band structure in germanium, my ass (2000)

#16

As an odd coincidence, I did the same experiment on a shoestring budget with substandard equipment also. I too used a fancy computer algorithm to get a best fit. Except that I managed to get four significant decimal places in the result — an improvement over the (also outdated) textbook. The author of the angry rant had a life-defining experience of overwhelming frustration. The same scenario resulted in a positive l…

[deleted]

Re: Electron band structure in germanium, my ass (2000)

#18

This was my experience when doing some of measurements back while getting higher ed. Sometimes you just get random results that has no relation to what you expected to get based on theory (and not just theory, but common sense). They're not zero and not over the top, they're just useless.

Welcome to experimental science. In this case they actually knew what they were looking for. Once you actually start doing real science, the first difficulty is to understand if what you are observing is actually what to expect or not (and that is not always straight forward).

Re: Electron band structure in germanium, my ass (2000)

#20

The CS conclusion was worthy though

The double irony would be for the author to have persevered in physics and now hold several patents over solid state batteries that are going to revolutionize society and fix climate change, while their CS major friends just got fired by some GAFAM for not getting enough minimum-pay workers to click on funny cat memes.
Post reply on HN