# What is Band: Definition and 531 Discussions

Bánd is a village in Veszprém county, Hungary.

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1. ### Reproduce band structure Kagome Fermi-Hubbard using Python

We need to define a high symmetry point path in the Brillouin zone, we can choose: Gamma-K-M-Gamma My attempt: import numpy as np import matplotlib.pyplot as plt # lattice vectors a1 = np.array([1, 0]) a2 = np.array([-1/2, np.sqrt(3)/2]) a3 = -(a1 + a2) a = [a1,a2,a3] #high symmetry points...
2. ### I Bell's spaceship paradox

They concluded: "One may conclude that whenever a body is constrained to move in such a way that all parts of it have the same acceleration with respect to an inertial frame (or, alternatively, in such a way that with respect to an inertial frame its dimensions are fixed, and there is no...
3. ### B Atom energy band formation and electron allotment

This is actually a two-part question: 1) According to the Copenhagen Interpretation, atoms have energy bands but there's no explanation of how these bands are derived, or why they only form for protons/antiprotons. Any thoughts? 2) The Copenhagen Interpretation mentions that when an atom's...
4. ### Average Kinetic Energy of Electron in the Conduction Band

Hello, I've seen in a few books on solid state physics that one can deduce an expression for average K.E.: $$<\:K.E.>\:=E_c+3/2\:k_B\:T$$ from the following: $$<\:K.E.>\:=\:\frac{\int \:\left(E-E_c\right)g\left(E\right)f\left(E\right)dE}{\int \:g\left(E\right)f\left(E\right)dE}$$ I can't...
5. ### A Empirical tight-binding sp3s* band structure of semiconductors

I'm simulating on code the tight-binding sp3s* bandstructure of certain semiconductors, such as GaAs, AlP, InP, ZnSe, etc. with spin-orbit coupling at a temperature of T = 0 K but I'm having trouble at finding the corresponding spin-orbit splitting parameters. For example, I've found in this...
6. ### I How does diffusion of high energy electrons shift band structure?

When an n-type material comes in contact with a p-type material to form pn-junction, electrons with the highest energy in the conduction band will diffuse to the p-side to reach equilibrium so the entire band structure on n-side will shift down relative to p-side as described in the following...
7. ### Rubber Band Fumes: Is My Cake Inedible?

I just baked a cake, and accidentally left a rubber band around the cake tin (which was holding the greaseproof paper in place). Is the cake inedible due to fumes given off by the rubber band?? Thanks :)
8. ### I Number of lines in Band Structure

The general idea is that, number of bands=number of lines. For instance, AlAs primitive cell (one of each atom per cell) has 13 bands; that is outer most shells have 13 distinct energy values. (Al: one 3s + three 3p, As: five 3d + one 4s + three 4p) But when I calculate Band Structure through...
9. ### I Question about Electronic Band Structure

According to this Wikipedia entry: https://en.wikipedia.org/wiki/Electronic_band_structure the discrete energy levels of an isolated atom split into N levels in a macroscopic crystalline lattice (N being the number of atoms in the lattice) forming essentially continuous bands from the discrete...
10. ### I A problem with a figure related to band theory

Hi, All. In searching for images related to the introduction of band theory in solid sate physics I found this one: I would like to ask you if I am correct in thinking the increase in the number of splittings (in b) is misleading to students. Thank you all DaTario
11. ### I Valence and conduction bands in five band Hamiltonian

Hello, I have this band structure plot for five band Hamiltonian model. I want to know which bands are valence and which one is conduction bands. Also if they have any special name I like to know that. Thank you.
12. ### MATLAB Graphene band structure Matlab code

I have this code for 3D band structure of graphene but i can't understand why while graphene first brillouin zone is hexagonal but here a rectangle form of first brillouin zone is used?E0 = 0; % coloumb integral V = -2.7; % hopping integral [eV] acc = 1.41; % c-c bond length [Angstrom] lattice =...
13. ### Engineering Can the efficiency of a solar cell with a single band gap reach 100%?

I have tried looking up online with the photoelectric effect, it just mentioned the energy of the photon must have to equal to band-gap energy. Yet, it didn't mention if 100% can be reached in that case, or if a single bandgap makes any effect...
14. ### Am I the only one into this power melodic metal Australian band?

Ilium: What a band! Ausi ausi!
15. ### An accurate method to determine the band gap

Summary:: What is an accurate method to determine the band gap? What is an accurate method to determine the band gap?
16. ### Cooper pairs in a band diagram

Can we draw a Cooper pair in a band diagram? I know that Cooper pairs have very small energy (because they obey the Bose-Einstein statistics) but I was wondering if we could somehow plot in a band diagram and if yes how?
17. ### I What kx/ky Values Are Used for Graphene Band Structure Plots?

Hello, https://www.researchgate.net/figure/Top-Graphene-nanoribbons-with-zigzag-left-and-armchair-right-edges-with-disordered_fig1_258105786 With what kx/ky values are these band structures plotted? The energy dispersion of graphene is given by this , yet I am confused to what kx/ky value...
18. ### Band theory: effective mass and Hall's coefficient

Consider the following scenario. A material has the E-k band scheme as shown in the figure (extended scheme of zones). Could anyone give me a suggestion regarding the following : Electrical character of the material with the temperature. Sign of the Hall coefficient. Sign of the effective mass...
19. ### Does Teaching by Numbers Limit Understanding of Elasticity in Rubber Bands?

If you take a rubber band and fix it in a stretched position for an extended period of time, would it eventually lose its elasticity? If yes, then how can you calculate how long it would take until its elasticity decreases by a certain amount, say, fifty percent? If no, why not? How does the...
20. ### How to Measure and Calculate Band Gap of a Photovoltaic Device

Hi there! I bought a photovoltaic cell. I would like to learn its band gap at 300 K and 0 K. How can i measure band gap or calculate? I have already measured Temperature to Vmax values. I couldn't find any good information about this topic. Thanks.
21. ### I Solar flare: Help normalizing the Band function

I am trying to understand how to normalize a proton energy spectrum from a solar flare. The spectrum is given by the Band Function, and I cite the paper "Spectral Analysis of the September 2017 Solar Energetic Particle Events" by Bruno in 2019, link to paper. The equation number in the paper is...
22. ### Python Problem with coding the band structure of graphene nanoribbons

Hi, I have a Matlab code for calculating the band structure of graphene nanoribbon which is working fine, but I wanted to convert it to python and I've done it. I guess I made a mistake somewhere because the plot is totally wrong. Could someone check it for me, please?
23. ### Heat engine that uses a rubber band (Thermodynamics)

Nota that the path a to b is isothermal since J is proportional to L, then we can find the value of T_a and T_b using the equation of state and the figure. We have, $$J_0=\alpha L_0T_b$$ or $$T_b=T_a=\frac{J_0}{\alpha L_0}=T_0$$ Also, by...
24. ### Question about using the Lagrangian for a spinning rubber band problem

Hello, I am having trouble applying Lagrangian to this problem: A uniform thin circular rubber band of mass ##M ## and spring constant k has an original radius ##R##. Now it is tossed into the air. Assume it remains circular when stabilized in air and rotates at angular speed ##\omega## about...
25. ### I Are the electrons in the conduction band completely free?

I'm having trouble to understand why it's said that electrons in the conductor band are free while electrons in the valence band are not. I know by the Schrodinger equations that the trajectory of an electron inside a specific band and with a specific energy level is a probability. From what I...
26. ### I Energy of Conduction and Valence Band in Opposing Directions

Recently, I have been studying some solid-state physics and I came across this ##E-k## diagram online. Here's an image for reference to what I am referring to...
27. ### B Chemical Potential μ in Solids

There is the equation: μ= Eu +Eg/2 +3/4kβTln(mu/mc) Eg is the band gap, but I don't understand what Eu stands for and how we can calculate it? Could it be the valence band?
28. ### Ant and rubber band problem

why can't we use Cartesian coordinates and in which way to proceed?
29. ### Correct statement regarding the load vs length graph of a rubber band

Option (B) is wrong because energy should be received by rubber band when it is being stretched Option (D) is wrong because energy should be released by rubber band when it goes back to natural length The area between graph of stretching and contracting represents energy dissipated in rubber...
30. ### Energy band gap when there is an electric field

So I have just been taught this topic but this question seems to be one of a kind and I can't seem to figure it out. What I've learnt: When there is a positive electric field applied to the right, for example, the electrons that are free moving in a crystal (aka conducting band) will oppose...
31. ### B Conduction Band Filled: Can Semiconductor Act as Insulator?

At T = 0K, the valance band of a semiconductor is completely filled, and no current can flow, acting as an insulator. Is there every a situation where the opposite can occur, such that the conduction band is filled (and the valance band is completely empty) forcing the semiconductor to be an...
32. ### I Rubber band and a Merry Go Around

Maybe someone already did this experiment? We have rubber band stretched and attached to the fence of Marry Go Around. When Marry is not rotating we are oscillating rubber band vertically, and oscillation remains vertical. What would happen if we oscillate the rubber band vertically when Marry...
33. ### A Electronic band structure of iron superconductor BaFe2As2

how can I determinate the electronic structure of a multiband system? for example in the case of the superconductor BaFe2As2 , the electronic properties are as known dominated by 5 Fe d states at the fermi energy, so 5 bands cross the Fermi level and form 5 Fermi surface sheets (if we consider...
34. ### How does applying potential affect the energy band diagram for a diode?

Ref: http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/pnjun2.html Hyperphysics Asstr Why does the band diagram shift up or down when I apply potential? Why does it shift down when positive potential is applied? Professor said it's because electron has negative charge and so we consider...
35. ### Band structure of a 2deg including spin orbit coupling

first of all, I tried to obtain the energy eigenvalues of the Hamiltonian, by using the equation ##det(\hat H -\lambda \hat I)=0## ##\gamma V\delta(z)(\hat z \times \mathbf{p}) \cdot \sigma=\gamma V\delta(z)(p_x\hat j-p_y\hat i)\cdot(\sigma_x\hat i + \sigma _y \hat j)=\gamma...
36. ### Choosing a heater band for vacuum system bakeout

Hello, I'm trying to find the right wattage heater band for a cylindrical vacuum chamber that is stainless steel (304), ~2ft in length, ~0.5ft in diameter, and ~0.5 in thick. From a quick google search, I was able to calculate the required wattage for bring the chamber up to and constant at...
37. ### Force Required to Stretch a Rubber Band to a Certain Diameter

Summary: Looking of someone to double check my work on this design issue. I am posting this here because I am no longer a student, but it is similar to a simple homework problem Problem: I am designing a rubber-band like product for a client. He wants to take a durable rubber band and stretch...
38. ### Why is the band gap in alloys such as GaAs less?

In pure crystals,such as,in silicon and germanium,the band gap is more than that in compound semiconductors,such as,GaAs.Why is that so.

40. ### I Free electron gas band structure?

How can I see, by looking at a band structure if the substance in question can be viewed as a free electron gas (FEG) or not? What characterizes a FEG in a bandstructure plot? Thanks in advance!
41. ### I Understanding Band Structure Diagrams

Hi! I never really understood band structure diagrams. I think they represent the energy of an electron, with the given circumstances, at a k vector. Are the electrons only allowed to be on the lines here? Or can they also be in areas enclosed under/between certain lines? What are some...
42. ### B Valence band, conduction band

Hi, Could you please help me with the queries below? Question 1: Please have a look on the attachment, conduction_band2, or check the following link for better resolution http://imagizer.imageshack.us/a/img921/4356/vODcjh.jpg It says, "Figure 1–7 shows energy diagrams for insulators...
43. ### MHB How can the residual capitalization problem be solved with three factors?

The following was written for something other than this forum. But it has all the information needed to solve the problem so please do not let the way it is written bother you. The results of my answer below I believe was luck. Me just fooling around with the numbers but there has never been...
44. ### B Solve Relativistic "Bug on Band" Problem

The problem goes: ‘One end of a rubber band is attached to a wall. The free end is stretched away from the wall at a rate v. At time zero the band is length L0 and a bug starts crawling along, from the wall, at rate u. How long until the bug reaches the free end?’ (Typically u << v for...
45. ### A Silicon band structure for both ibrav 0 and ibrav 2

Silicon Band Structure for both ibrav 0 and ibrav 2 I did scf and bands for silicon using both ibrav=0 and ibrav 2 After running the two bands separately I noticed that the band structures for the two (ibrav 0 and ibrav 2) were totally difference but in literature i read that the two (both ibrav...
46. ### A Band Gap Vs Pressure: Proskite Compounds

why band gap reduces when pressure increased for provskite compounds ? Nawzad
47. ### Band diagram, conductivity tensor

Hello! Does anyone have an idea of how can I obtain information from a band diagram about the directions along which the system conducts best and worst ? Thank you in advanced! :)
48. ### Semiconductors - Flat band Diagram vs Equilibrium Diagram

Homework Statement Homework Equations Energy band diagram equations. The Attempt at a Solution This is more of a conceptual question, but this is the problem I am working on for reference. What is the difference between a flat band diagram and an equilibrium diagram? I know what they will...
49. ### I Valence band and Fermi level difference?

I was wondering what the difference was between the valence band and fermi level? How do we distinguish between the two? Thanks in advance.
50. ### Understanding solar cell band diagram

Hi everyone, I have been studying the physics of solar cells for a long time. The only thing that I can not completely understand is the physical operation of solar cell based on band diagram. Can anyone briefly explain the movements of carriers from one electrode to the another based on band...