Which solid configuration has the highest density of states for electrons?

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Discussion Overview

The discussion revolves around the density of states available to electrons in different solid configurations, specifically comparing polycrystalline iron, quartz, and semiconductors. Participants explore the implications of electron states in solids, including the transition from discrete energy levels to energy bands, and the factors influencing the number of available states.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants inquire about which solid configuration—polycrystalline iron, quartz, or semiconductors—has the most available electron states and the ease of changing those states.
  • There is a discussion on how electrons in isolation have discrete energy values, while in solids, these values form energy bands that allow for a greater number of states.
  • One participant argues that the question is ill-posed, noting that while individual atoms have infinite states, the transition to solids complicates the comparison of densities of states.
  • Another participant challenges the notion of discrete values for free electrons, suggesting that they do not possess discrete energy levels when not influenced by external potentials.
  • Concerns are raised about the ambiguity of the question regarding total states versus density of states, emphasizing the need for clarity on relevant energy bands and momentum ranges.
  • It is noted that changing the crystal structure of a solid can affect its density of states, indicating that the question cannot be answered by simply naming a material.

Areas of Agreement / Disagreement

Participants express differing views on the formulation of the question and the implications of density of states. There is no consensus on which solid has the highest density of states, and the discussion remains unresolved regarding the criteria for comparison.

Contextual Notes

Participants highlight limitations in the question's formulation, including the need for specific definitions of relevant energy bands and the impact of crystal structure on density of states.

cube137
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With regards to the number of states available to the electrons in these solids.

1. a mass of polycrystalline iron (plenty of free electrons)
2. quartz (has practically no free electrons).
3. semiconductors

Which of them has the most number of states available to the electrons?
Which has the most ease of getting them to change states considered against the ease with which they change states by themselves?
 
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To rephrase it. An electron in isolation has discrete value. When it is part of solid, The formerly discrete nature of allowed energies for an electron is turned into thick energy bands, within which electrons can occupy any energy they desire (well, almost). In this sense, you have many states available to the electrons.

Which of these... iron, quartz or semiconductors have most states available to the electrons?

What other solid configuration has the most states available to the electrons?
 
This is an ill-posed question. If you look at hydrogen atoms, the allowed bound states have energies equal to ## E_n = \frac {Ry} {n^2} ## and n is the main quantum number ranging from 1 to ... infinity. In other words, there is an infinite number of available electronic states in a single hydrogen atom. It is true for any atom as well. Now, when atoms form a solid, each of these atomic state is split into a band and within each band, there are as many allowed states as there are atoms in the entire solid (ok, strictly speaking, each band has as many states as there are primitive unit cells within the entire solid but number of bands gets multiplied by number of atoms within a primitive unit cell).
So, you have an infinite number of states multiplied by a very large number of atoms in a piece of solid.
Which infinity is greater?
 
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cube137 said:
To rephrase it. An electron in isolation has discrete value.

This is false. If you mean an electron "in isolation" as in free electron (i.e. not encumbered by any external potential), then it does not have "discrete values" in terms of the allowed energies and momentum. Try it. Solve the Schrödinger equation for a free electron.

When it is part of solid, The formerly discrete nature of allowed energies for an electron is turned into thick energy bands, within which electrons can occupy any energy they desire (well, almost). In this sense, you have many states available to the electrons.

See your mistaken idea above.

Which of these... iron, quartz or semiconductors have most states available to the electrons?

What other solid configuration has the most states available to the electrons?

As has been stated, this is an ill-posed question. If you are talking about the density of states, then that's a different issues, because you will have to indicate the relevant bands and relevant energy and momentum range. Asking for a total number of states does not make sense.

And not only that, even for a particular solid, such as iron, changing its crystal structure can change its density of states. So just specifying an element alone, or a semiconductor alone, isn't sufficient.

Zz.
 
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