Pressure-induced charge transfer reversal in Ba-Te compounds

Abstract Under high pressure, the 5 d orbitals and/or electrons of barium (Ba) atoms can be activated, demonstrating electronic properties distinct from those of alkaline earth metals under ambient conditions. This work indicates that Ba's 5 d band can even capture electrons from tellurium (Te) atoms exhibiting anionic characteristics under high pressure using first-principles calculations combined with CALYPSO structure prediction. At 397 GPa, a charge transfer reversal takes place within the compound, with Ba atoms gaining electrons and exhibiting anionic behavior, while Te atoms lose electrons and display cationic characteristics. Further projected density of states (PDOS) analysis reveals that the pressure broadens the Ba's 5 d and Te's 5 p bands significantly, and the 5 d band shifts below the Fermi level and becomes partially occupied, while the 5 p band moves above the Fermi level, creating unoccupied states. This work predicts two new stable polymorphs of BaTe 4 , while the remaining Ba-Te compounds are reproduced from previous studies and serve as the basis for our electronic structure and bonding analyses. Our findings demonstrate the complex chemical nature of Ba under high-pressure conditions.