# Tag Info

Accepted

### Fermi energy lower than valence band maximum?

No, this isn't possible for an undoped semiconductor. The reason it's happening is because the Fermi level is not well defined for your semiconductor at finite temperature, and you're trying to read ...
• 8,052
Accepted

### Cohesive Energy of a metal oxide

Calculate the total energy of the unit cell. Take each unique atom from your unit cell and calculate its energy in isolation. Take the full unit cell energy and subtract off the energy of each lone ...
• 940
Accepted

### Can a material be a conductor in one direction and a semiconductor in another direction?

If I understand your question, the answer is yes. Really, the only requirement is anisotropy. Consider e.g. a half-filled 1d chain. It is metallic along the chain and insulating perpendicular to it. I ...
• 1,543

### Effect of carrier concentration on electrical conductivity

In case someone else starts wondering on the same phenomenon, what I figured out is as follows. When observing the band structure of the material, it should be noted that only electronic states with ...
• 2,653

### What does it mean if the Fermi level crosses into the valence band? How about into the conduction band?

The 0-energy outputted by QE does not necessarily correspond with the Fermi energy. Depending on what keywords you use in your input, you can get the actual Fermi-energy outputted - you should try ...
• 628

### Which software to model Fermi level position of graphene in an external electric field?

SIESTA With SIESTA and its TranSIESTA module, you can model all you are looking for. From the SIESTA site: SIESTA is both a method and its computer program implementation, to perform efficient ...
• 23.6k

### How to interpret defect formation energy diagram?

Why defect formation energy is plotted against $E_F:$ Let's go step-by-step. First, let us look at the Defect Formation Energy (DFE) formula:  E_f^D(q,E_F) = E^D(q)-E^{\mathrm{host}}-\sum n_i\mu_i + ...

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