Energy curve plotter
"Better" is obviously fairly subjective. After a quick glance I would like to make a few suggestions:


If you already imported scipy, you don't need to import
scipy.optimize separately. You can either limit the importing by just
importing the (sub)modules you need, which is cleaner. Or you can
import the entire module and just use what you need.
Especially in terms of usability and readability for later (especially rereading your own code), I would suggest adding some docstring to describe what it does: https://www.python.org/dev/peps/pep-0257/#id16
Similarly I would use a clearer naming convention. The program won't run faster if you call it "energy_curve_calculator_function_using_curve_fit" or "f", but when you look into your files, you will know the difference. 
Lastly, I would also advise you add a comment block (or one line) between each section of code explaining what it does.


Right now pep8 only checks that your lines aren't too long. I would concentrate a little more on making sure someone who didn't write the code (or you in a few months) can read what it's doing based on the flow, comments where needed and the variable names.