Help for supercell, Bloch function

  • Context: Graduate 
  • Thread starter Thread starter jhzhou2010
  • Start date Start date
  • Tags Tags
    Function
Click For Summary
SUMMARY

The relationship between the periodic part of the Bloch function in a primitive cell, denoted as u_nk(r), and that in a supercell is defined by the transformation of the wave vector k. In a supercell that is three times longer than the primitive cell, the wave vector k transforms to k' + K, where K can take on three specific values: 0, 2π/3d, and 4π/3d. This results in the equation u'_{nKk}(x) = u_{nk}(x) exp(iKx), establishing a clear mathematical relationship between the two functions.

PREREQUISITES
  • Understanding of Bloch's theorem and wave functions in solid-state physics.
  • Familiarity with the concepts of primitive cells and supercells in crystallography.
  • Knowledge of reciprocal lattice vectors and their significance in band structure calculations.
  • Basic grasp of mathematical notation used in quantum mechanics and solid-state physics.
NEXT STEPS
  • Study the implications of supercell calculations in density functional theory (DFT).
  • Explore the mathematical derivation of Bloch's theorem in various lattice structures.
  • Learn about the effects of periodic boundary conditions on electronic band structure.
  • Investigate the role of symmetry in determining the properties of supercells.
USEFUL FOR

Physicists, materials scientists, and computational chemists who are involved in solid-state physics research, particularly those working with electronic band structure and crystal lattice simulations.

jhzhou2010
Messages
2
Reaction score
0
I recently have a puzlle that what is the relation between the periodic part of Bloch function in primitive cell u_nk(r) and that in supercell, e.g., three primitive cells in one of the directions. Are they the same one?



pls give me some hints or explanations!


thanks~~
 
Physics news on Phys.org
Well, the unit cell in the reciprocal lattice is smaller in the case of supercells than in the case of normal cells in direct lattice. That is the vector k for the normal lattice will become k'+K in case of the supercell lattice where K may take on 3 values in the case of a supercell which is 3 times longer than a normal cell.
Hence
[tex]u_{nk}(x)\exp(ikx)=u'_{NKk}\exp(ik'x)[/tex]
or
[tex]u'_{nKk}(x)=u_{nk}(x)\exp(iKx)[/tex]
If the length of the original unit cell is d and the length of the supercell is 3d (at least for a space group with orthogonal axes)
then [tex]K \in \{0,2\pi/3d,4\pi/3d\}[/tex].
 
Thanks very much for your useful reply!
 

Similar threads

  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 20 ·
Replies
20
Views
7K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 3 ·
Replies
3
Views
6K
  • · Replies 13 ·
Replies
13
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K