I recommend using Google: if you type "quantum chemical software" the first hit is a list will all kinds of them. It contains a column named 'License' where you can see if its free or not.

https://en.wikipedia.org/wiki/List_of_quantum_chemistry_and_solid-state_physics_software

Dear Professor Fernando Vallejos-Burgos,

First of all, thank you very much for your answer. I agree with you. However, I meant two main things. (1)If the program has been tried by some of you already then you will have good experience with that program. Therefore that (those) program(s) will be reliable in our scientific research.

Some programs have very specific web sites to download and other web sites might be fake.

Thank you again for your good sharing.

All the best,

Mostafa

I think if quantum expression and abinit can be used, they are free and very reliable.

I have tried abinit for band gap calculation in bulk but not sure whether it can also calculate for nano-materials.

Thank you so much Professor Homnath Luitel for your good sharing.

Indeed, I do appreciate that.