  A combination of $^{19}$F magic angle spinning (MAS) nuclear magnetic
resonance (NMR) and density functional theory (DFT) were used to study the
ordering of F atoms in Pb$_2$Ti$_4$O$_9$F$_2$. This analysis revealed that F
atoms predominantly occupy two of the six available inequivalent sites in a
ratio of 73:27. DFT-based calculations explained the preference of F occupation
on these sites and quantitatively reproduced the experimental occupation ratio,
independent of the choice of functional. We concluded that the Pb atom's 6$s^2$
lone pair may play a role ($\sim$0.1 eV/f.u.) in determining the majority and
minority F occupation sites with partial density of states and crystal orbital
Hamiltonian population analyses applied to the DFT wave functions.
