# Recent content by Foder

1. ### Bravais Lattice in Two Dimensions

3D have more point groups than 2D because of the extra degree of freedom. I mean, point groups represent symmetry operations, such as inversions, reflections and rotations. When you add an extra dimension you can perform those in new directions not parallel to the original 2D plane, allowing...
2. ### Bravais Lattice in Two Dimensions

I believe there are 32 point groups in 3D.
3. ### Difference between Primitive cell, unit cell and a wigner-seitz cell.

Each corner point of a cubic cell is shared by 8 identical contiguous cubic cells hence, for each one of these cells corresponds 1/8 atom (or molecule or whatever). There are 8 corners per cubic cell, then we got the 1/8 * 8. Each atom located at the faces of a cubic cell is shared by 2...
4. ### Does metal coating on porous silicon have any effect on band structure?

Yes, there can surely be changes in band structure, specially in the interface, where the interaction between Si electrons with the metalic particle is stronger.
5. ### Difference between Primitive cell, unit cell and a wigner-seitz cell.

WZ is the smallest possible primitive cell, but that doesnt mean that it is always appliable/representative of the crystal. For example, in a system with two different elements you can build the WZ but it won't be a primitive cell, in the sense that with only one kind of atom you cannot...
6. ### What is the meaning of k in E(k) diagram?

E(k)=(hbar*k)^2/(2m)+Vo In the E(k) diagrams (dispertion curve) E can be considered as the kinetic energy only, but the zero energy value corresponds to the potential energy Vo, so, it's not actually zero.
7. ### Difference between Primitive cell, unit cell and a wigner-seitz cell.

Hello, here is the answer: Unit cell: volume formed by the arbitrary chosen basis vectors (normally within the 14 Bravais systems). They fill the complete space by translational symmetry. Primitive cell: smallest possible unit cell. Wigner-Seitz cell: smallest possible primitive cell, which...
8. ### Conduction mechanism of SnO2 semiconductors

Hello everybody and welcome to my first thread. I have read several publications regarding this compound, and found that SnO2 behaves as n-type semiconductor (Eg 3.6 eV) when oxygen vacancies are present. Very summarized and simply put, I understood that this lack of oxygen atoms enhance the...