Phonon dynamics in (Bi2Se3)m(Bi2)n infinitely adaptive series

• The evolution of phonon structures with different ratio of m:n is discussed.
• The observed shift of Raman modes experimentally is reproduced well by calculation.
• The origin of phonon shift is due to change of type of interaction between blocks.
• Thermoelectric performance is discussed combining our calculations.

The(Bi2Se3)m(Bi2)n infinitely adaptive series derived from stacking hexagonal Bi2 and Bi2Se3 blocks have been found to be topological insulators. Its structures and phonon dynamics are calculated from density-functional perturbation theory by including spin–orbit coupling. Full phonon dispersion curves and phonon density of states with different ratio of m:nm:n are calculated and the zone-center Raman active modes are analyzed. The shift of phonon frequency of Raman modes observed experimentally for Bi-rich sample is reproduced well by our calculations and its origin is discussed. The large mismatch of phonon density of states between Bi2Se3 quintuple layer and Bi bilayer implies that thermoelectric performance for slightly Bi-rich sample might have a significant improvement due to the reduction of thermal conductance.