Polynomial Potential

Hello everyone. I am trying to model one of my oxides using a polynomial potential with n C0, C1, rmin rmax terms. Does anyone have an example input file for this? I’m not sure what the correct format would be.

Many thanks,

Hi Ali,
I’ll go one better than just giving you the answer - I’ll explain a method that allows you solve such problems independently:

  1. Obvious the starting point is to look at the help to get the basic format:
    GULP help file

  2. If something isn’t clear then you can easily test whether your input is right. Create a dummy system with 2 atoms only at a distance of 2 Angstroms (doesn’t matter what it is really). You then create the input for the potential and just make one coefficient of the polynomial non-zero at a time and calculate a single point energy. You can then compare what comes out from GULP with the value you calculate in your head (for a polynomial since it’s trivial to do) and if you get the right energy then you’ve got the right input.

The same approach works for any potential and allows you to check your input is correct very easily.