On the other hand, the poorer energy match between the Bi 6s and Se 4p/Te 5p leads to weaker orbital interactions that are insufficient to stabilize an active lone pair, resulting in "quenching". Bi2Se3 and Bi2Te3 therefore preferentially adopt the higher-symmetry R3 ̅ m phase. relatively high energies, we therefore conclude that these phases are highly unlikely to be formed under ambient conditions. The dynamical stabilities of the eight structures, assessed from the presence or absence of imaginary modes in the calculated phonon dispersions, are collected alongside the relative energies in Table .