Exercise 1 - Better Total G(r)

We saw how to improve agreement between the experiment and simulation by modifying the equilibrium distance of the Cu–O master bond in the forcefield. How much better can we make the agreement?

Here we’ll focus on the peak around 2.8 Å, whose assignment is as follows:

The peak appears to be associated to the proximity of the C(3) and O atoms in the structure, and which essentially are connected by a torsion interaction C3–C2–C1–O. The central interaction C2–C1 is the bond connecting the carboxylate group to the benzene ring. So how can we improve (reduce) the distance between the C3 and O atoms at the termini of this interaction?

One possibility is to change the equilibrium bond distance of the middle C2–C1 in order to push the C3 and O atoms apart. But what effect will this have on other parts of the structure as represented by the G(r) and, indeed, the F(Q)?