Prediction of the Topologically Nontrivial Phase in Three-Dimensional ABX Zintl Compounds.

Zintl compounds have garnered research interest due to their diverse technological applications. Utilizing first-principles calculations, we performed a systematic study of ABX (A = Li, Na, K, Rb, or Cs; B = Si, Ge, Sn, or Pb; and X = P, As, Sb, or Bi) Zintl materials with the 6 KSnSb-type structure. Notably, six ABX Zintl compounds (RbSiBi, CsSiBi, LiGeBi, KGeBi, RbGeBi, and CsGeBi) were found to have topologically nontrivial phases, as demonstrated by the invariant computed using the hybrid functional HSE06. Among them, RbGeBi and CsGeBi were identified as topological insulators with nontrivial bandgaps of 28 and 116 meV, respectively. The topological phase transition arises as a result of spin-orbit coupling, as demonstrated in the representative material, CsGeBi. Additionally, the existence of gapless surface states further confirmed the topologically nontrivial phases of the six materials. Moreover, phonon spectra and formation energy calculations verified that all identified nontrivial materials under the hybrid functional are dynamically and structurally stable, except LiGeBi which exhibited imaginary phonon frequencies. Finally, the thermodynamic stability of the representative material CsGeBi was verified through elastic constants and ab initio molecular dynamics simulations. These results provide foundational insights that could drive further experimental research and synthesis, potentially enabling the application of ABX Zintl compounds in electronic technologies such as quantum computing or spintronics.