Exchange-correlation functional effects on electronic and phononic band structures of helical Se and Te

초록

Trigonal selenium (Se) and tellurium (Te), with their one-dimensional helical structures, exhibit unique chiralitydriven physical phenomena. Here, we systematically investigate the influence of various XC functionals-ranging from conventional generalized gradient approximations (GGA) and meta-GGA to hybrid functionals-on the electronic and phononic band structures of Se and Te. Our calculations reveal that while meta-GGA functionals provide little improvement in electronic structures over conventional GGA, the hybrid functional HSE06 predicts a significant widening of the electronic band gap. This effect is attributed to an enhanced charge localization within the intra-chain covalent bonds, more evident in trigonal Se than in Te. Moreover, the strengthened intrachain bonding in the HSE06 calculation leads to a hardening of high-frequency intra-chain modes and a softening of low-frequency inter-chain modes. Remarkably, trigonal Se exhibits an unusual anharmonic hardening of high-frequency optical modes under isobaric conditions, originating from the large disparity between strong intrachain and weak inter-chain force constants.

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