Why is the volume of FCC and BCC different in reciprocal space?

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SUMMARY

The discussion clarifies the differences in volume between Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC) structures in reciprocal space. In BCC, the total volume is calculated as 4 times the cube of the reciprocal lattice length, resulting in a volume of 4(2π/a)³. Conversely, for FCC, the volume is 2(2π/a)³. The confusion arises from the transformation of unit cells between real and reciprocal spaces, emphasizing the importance of understanding the relationship between lattice structures and their corresponding volumes.

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  • Understanding of crystal lattice structures, specifically BCC and FCC.
  • Familiarity with reciprocal lattice concepts in solid-state physics.
  • Knowledge of unit cell volume calculations in crystallography.
  • Basic grasp of vector mathematics related to lattice vectors.
NEXT STEPS
  • Study the derivation of unit cell volumes for BCC and FCC structures.
  • Learn about the transformation of real space lattices to reciprocal space.
  • Explore the implications of lattice symmetry on physical properties.
  • Investigate the significance of reciprocal lattice vectors in diffraction patterns.
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Students and professionals in materials science, solid-state physics, and crystallography who seek to deepen their understanding of lattice structures and their properties in reciprocal space.

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Taken from http://dao.mit.edu/8.231/BZandRL.pdf

BCC

In real space, it has a simple cubic lattice with one basis in the centre. Total number of atoms per unit cell = 2. Volume of primitive unit cell is then ##\frac{1}{2}a^3##.

In reciprocal space, BCC becomes an FCC structure. It has a simple cubic lattice of length ##\frac{2\pi}{a}## with 4 atoms in total. Why is the total volume then ##4 \left(\frac{2\pi}{a}\right)^3## and not ##\frac{1}{4}\left(\frac{2\pi}{a}\right)^3##?
FCC
In real space, it has a simple cubic lattic with 3 basis. Total number of atoms per unit cell = 4. Volume of primitive unit cell is then ##\frac{1}{4}a^3##.

In reciprocal space, FCC becomes a BCC structure. It has a simple cubic lattice of length ##\frac{2\pi}{a}## with 2 atoms in total. Why is the total volume then ##2 \left(\frac{2\pi}{a}\right)^3## and not ##\frac{1}{2}\left(\frac{2\pi}{a}\right)^3##?
 
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What is the the magnitude of the unit vectors of the reciprocal lattice? I don't think the size of the reciprocal cube for BCC is 2pi/a.
 

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