Piezochromic effects and low-pressure superconductivity discovered in inorganic halide perovskite RbPbI₃

The structural phase evolution and superconductivity of perovskite RbPbI3 under pressure have been investigated by employing first-principles calculations. The findings suggest that RbPbI3 undergoes three structural phase transitions from ppPv-Pnma to ppPv-Pnma(I) phases at 4.6 GPa, from ppPv-Pnma(I) to ppPv-Pnma(V) phases at 19 GPa, and from ppPv-Pnma(V) to Pm phases at 69.2 GPa, respectively. Two novel phases ppPv-Pnma(V) and Pm are predicted, differing from previously reported results. Meanwhile, an obvious piezochromic effect appears in the ppPv-Pnma(I) phase due to the change of the band gap under pressure tuning. Quite surprisingly, the electron-phonon coupling calculations reveal that the ppPv-Pnma(V) phase may be a potential low-pressure superconductor with a T-c of 8 K (7.3 K) at 20 GPa, which is slightly higher than those of other similar perovskites or alloys (similar to 3 K). Our studies further provide theoretical support for exploring high-T-c low-pressure superconductivity and piezochromic effects in halide perovskites.