First-principles Study On Structure And Properties Of Heavy Metal Halides

Ternary alkali metal halides and binary metal halides have good electronic and optical properties and have potential applications in semiconductor devices,photodetectors,and solar cells.1.We present a theoretical study on new phase searches,structural stability,pressure induced phase transition and photocatalytic properties in RbPbCl3 using first-principle calculations guided by the developed crystal structure analysis by particle swarm optimization(CALYPSO)methodology.Four new phases of P4/mmm,C2mm,I4mm and Cm of RbPbCl3 are predicted and the phonon spectra show that all the four phases are thermodynamically and dynamically stable.The calculated results indicate that the four phases are semiconducting and the contribution of edge states mainly comes from the Pb-Cl chains.Besides,the comparison of the band gaps show that pressure can regularly modulate the electronic structural properties for a certain phase.Meanwhile,the band alignments show that C2mm,14mm and Cm phases are promising candidates for the properties of photocatalytic water splitting.2.The structural,electronic and photocatalytic properties of five vacancy-containing 2D BiI3 monolayers are investigated by the first-principle calculations.The electronic structures show that the five structures are stable and have comparable binding energies to that of the pristine Bil3 monolayer,and the defects can tune the band gaps.Optical spectra indicate that the five structures retain high absorption capacity forvisible light.The spin-orbit coupling(SOC)effect is found to play an important role in the band edge of defective structures,and the VBi and VBi-I3 defective Bil3 monolayers can make absolute band edges straddle water redox potentials more easily.