  The hybrid halide perovskites MAPbI$_{3}$, MAPbI$_{2.94}$Cl$_{0.06}$, and
MAPbCl$_{3}$ (MA - methylammonium) have been investigated using inelastic and
quasielastic neutron scattering (QENS) with the aim of elucidating the impact
of chloride substitution on the rotational dynamics of MA. In this context, we
discuss the influence of the inelastic neutron scattering caused by low-energy
phonons on the QENS resulting from the MA rotational dynamics in
MAPbI$_{3-x}$Cl$_{x}$. Through a comparative temperature-dependent QENS
investigation with different energy resolutions, which allow a wide Fourier
time window, we achieved a consistent description of the influence of chlorine
substitution in MAPbI$_{3}$ on to the MA dynamics. Our results show that
chlorine substitution in the low temperature orthorhombic phase leads to a
weakening of the hydrogen bridge bonds since the characteristic relaxation
times of C$_{3}$ rotation at 70 K in MAPbCl$_{3}$ (135 ps) and
MAPbI$_{2.94}$Cl$_{0.06}$ (485 ps) are much shorter than in MAPbI$_{3}$ (1635
ps). For the orthorhombic phase, we obtained the activation energies from the
temperature-dependent characteristic relaxation times ${\tau}$C$_{3}$ by
Arrhenius fits indicating lower values of E$_{a}$ for MAPbCl$_{3}$ and
MAPbI$_{2.94}$Cl$_{0.06}$ compared to MAPbI$_{3}$. We also performed QENS
analyses at 190 K for all three samples. Here we observed that MAPbCl$_{3}$
shows slower MA rotational dynamics than MAPbI$_{3}$ in the disordered
structure.
