This depends on what you want to do. Temperature factors represent the thermal vibration amplitude of atoms about their equilibrium positions. These vibration amplitudes can influence XRD patterns amongst other material properties.

Which properties of solid state calculations are really effected by temp. factors. Is there any change in the electronic properties seen due to the temp. factors?

What system and properties are you looking at specifically? Do phonons play a role in that property? Electrical conductivity of metals, for example, is related to phonon properties.

If you are unsure, play it safe. I would highly recommend you at least run your calculations with different temperature factors as to see if results are changed.

-David

It is fine. Does the electrical conductivities for some non metallic semiconductors also depend on phonons. Also how could I add temp. factors fo the system. It should be added in the form of isotropic and anisotropic temp. values. But how could I predict them for each atom theoritically, if the structure is not reported.

Your first place should be experimental XRD patterns, which often include temperature factors in the analysis of XRD peak decay. But it sounds like that is not an option for you, so you could determine them with MD simulation as well. Sometimes, temp. factors are taken from data on atoms in similar materials, but I would not recommend this at all if quantitative accuracy is needed.

You could also use an approach like this:

http://ematweb.cmi.ua.ac.be/emat/pdf/1556.pdf

Also, please see such materials as this to consider phonon influence on conductivity:

http://ecee.colorado.edu/~bart/book/book/chapter2/ch2_7.htm