  We examine the ionic migration of Li in LATP [$\text{Li}_{1+x} \text{Al}_x
\text{Ti}_{2-x} {(\text{P} \text{O}_4)}_3$] solid electrolytes from an
atomistic viewpoint by means of density functional theory calculations. We vary
the Al content and investigate its effects on the crystal structure of LATP and
on the migration energy landscape of interstitial Li ions. The energy profiles
governing the Li diffusion are found to be systematically influenced by the
position of Al ions in direct vicinity of the migration path, and we derive a
simplified classification scheme of three universal energy profile shapes. The
overall influence of the Al/Ti-ratio on the Li migration is analyzed by a
separation into chemical and geometrical aspects. This work provides a solid
basis for a resource-efficient computational examination of the ionic
conductivity of Li in LATP with varying Al/Ti concentrations.
