How Do You Calculate the Effective Mass of Electrons in a Kronig-Penney Model?

(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1
  • #1
fighterflyer
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Homework Statement


Consider electrons in a Kronig-Penney model with the following parameters:
a=b=3 angstroms
Uo=10.0 eV

Calculate the effective mass of the electrons near the start of the first allowed band.

You can find this by fitting the E-k results to an equation

E=E1+(hbar^2 x k^2)/(2m*) where E1 is the start of the first allowed band.

Homework Equations





The Attempt at a Solution



I have no clue where to start. Since I'm trying to find m*, it will probably be in relation to E, so how do I calculate E from the given values?
 
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  • #2


To calculate E, we can use the Kronig-Penney model to find the allowed energy levels for the electrons. The model describes the potential energy of the electrons in a periodic potential, such as a crystal lattice. In this case, the potential is described by the parameters a, b, and Uo.

To start, we can use the Schrodinger equation to determine the allowed energy levels for the electrons. The equation for a one-dimensional Kronig-Penney model is:

cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin(kb) = cos(ka)cos(kb) - (1/2)*(ka + kb)*sin(ka)sin
 

1. What is effective mass and why is it important in scientific calculations?

Effective mass is a concept used in physics and materials science to describe the behavior of electrons in a solid material. It represents the mass of an electron as it moves through a crystal lattice, and is important because it helps us understand the electrical and thermal properties of materials.

2. How is effective mass calculated?

Effective mass is calculated using the band structure of a material, which describes the relationship between energy and momentum of electrons in the material. It involves taking the second derivative of the energy with respect to the momentum in a specific direction.

3. What factors influence the effective mass of electrons in a material?

The effective mass of electrons can be influenced by a variety of factors, including the crystal structure of the material, the presence of impurities or defects, and external factors such as temperature and pressure.

4. Can effective mass be negative?

No, effective mass cannot be negative. It is a positive value that represents the inertia of an electron as it interacts with the crystal lattice of a material.

5. How does effective mass affect the electrical conductivity of a material?

Effective mass is directly related to the electrical conductivity of a material. Materials with lower effective mass tend to have higher electrical conductivity, as electrons can move more freely through the crystal lattice. This is why metals, which have low effective mass, are good conductors of electricity.

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