plot [R=200:400] repulsion(R), attraction(R),pe(R)

(plot in the range R=200 pm to 400 pm the terms repulsion(R), attraction(R) and pe(R))

This will produce a third window, containing the plot. You can choose which window is active by moving the cursor into it.

The forces we are looking at are very weak and so it is useful to alter the units of the energy to J mol^-1 instead of kJ mol^-1.

We can do this simply by telling the graph plotter to multiply the y-axis of the plots by 1000.

plot [R=200:400] repulsion(R)*1000, attraction(R)*1000,pe(R)*1000

Finally, we can add labels to the axes and add a title.

set xlabel "R/pm"

set ylabel "Energy/Jmol-1"

set title "Total van der Waals Energy and contributions"

replot