  The potential energy landscape (PEL) of supercooled binary Lennard-Jones
(BLJ) mixtures exhibits local minima, or inherent structures (IS), which are
organized into meta-basins (MB). We study the particle rearrangements related
to transitions between both successive IS and successive MB for a small 80:20
BLJ system near the mode-coupling temperature T_MCT. The analysis includes the
displacements of individual particles, the localization of the rearrangements
and the relevance of string-like motion. We find that the particle
rearrangements during IS and MB transitions do not change significantly at
T_MCT. Further, it is demonstrated that IS and MB dynamics are spatially
heterogeneous and facilitated by string-like motion. To investigate the
mechanism of string-like motion, we follow the particle rearrangements during
suitable sequences of IS transitions. We find that most strings observed after
a series of transitions do not move coherently during a single transition, but
subunits of different sizes are active at different times. Several findings
suggest that the occurrence of a successful string enables the system to exit a
MB. Moreover, we show that the particle rearrangements during two consecutive
MB transitions are basically uncorrelated. Specifically, different groups of
particles are highly mobile during subsequent MB transitions. Finally, the
relation between the features of the PEL and the relaxation processes in
supercooled liquids is discussed.
