I am trying to fit an interatomic potential for the Buckingham-Coulomb form of an energetic material TKX-50. The molecular formula in C2H8N10O4. I am using Orca for quantum level calculation ( ab initio and dft). By applying RESP population I have determined the partial atomic charges for the molecule.
I am new in GULP. So what information do I need to find from the quantum calculation to set as observables to fit the Buckingham-Coulomb potential for my material?
This isn’t really a question specific to GULP, but more about the design of the research project as there are different approaches to fitting data based on either the energy surface, or the equilibrium structure and curvature. There are examples of both provided with GULP. I’d recommend reading the Phil. Mag. B paper in the GULP background references where it discusses fitting methods.