# A query on density functional theory (DFT)?

I know this is not the best forum to ask this question (but I think it is a pretty good one).

I have a fundamental confusion regarding DFT. In DFT all the calculations are performed using crystal structures at 0 kelvin, aren't they?

If yes, then consider the situation when we have a material which undergoes a phase transition at a certain temperature $$T_{c}$$ > 0 K. So above $$T_{c}$$ the material has different crystal structure than at 0 K. Now suppose we want to find out a particular property of the material at a temperature $$T$$ > $$T_{c}$$. To study the property using DFT we use a DFT code like Quantum Espresso and the crystal structure of the material at 0 K. So my question is :

Why/How is it okay to use the crystal structure at 0 K which is different from the structure of the material at the temperature we are concerned with? (Sorry for the confusing language)