Significance of electron temperature (broadening)

[neha_kapila]

I have a doubt that during the simulations we set the electron temperature (broadening) if the value is high convergence of calculations is fast. But I observed change in the band structure as increasing the temperature from 300K to 1000K, so can we say these calculations are above room temperature calculations? If not that tell me the procedure to do room temperature calculations.

[henrique_miranda]

The complete answer to your question is rather involved.

I will just summarise a few of the main points here:
1. Electronic broadening in a sense is related to the temperature of the electrons (see https://journals.aps.org/pr/abstract/10 ... .137.A1441)
2. A typical DFT calculation assumes the ions are frozen in their positions. This is not true even at T=0 because of quantum fluctuations. Furthermore, as the temperature of the system increases the ions move even more around their equilibrium positions.

So when you change the broadening you are accounting for the temperature of the electrons:
https://www.vasp.at/wiki/index.php/K-po ... ng_methods
If you want to include the temperature of the ions you might treat them classically for example with a molecular dynamic simulation:
https://www.vasp.at/wiki/index.php/Cate ... r_dynamics
If you are considering low temperatures you might need to consider quantum effects for example:
https://www.vasp.at/wiki/index.php/Elec ... o_sampling

There are many other approaches to include the quantum fluctuations of the ions which you can find in the literature