The electronic structures of cubic structure of ABX3（A=CH3NH3, Cs; B=Sn, Pb; X=Cl, Br, I） are analyzed by den- sity functional theory using the Perdew-Burke-Ernzerhof exchange-correlation functional and using the Heyd-Scuseria- Ernzerhof hybrid functional. The valence band maximum （VBM） is found to be made up by an antibonding hybridization of B s and X p states, whereas bands made up by the π antibonding of B p and X p states dominates the conduction band minimum （CBM）. The changes of VBM, CBM, and band gap with ion B and X are then systematically summarized. The natural band offsets of ABX3 are partly given. We also found for all the ABX3 perovskite materials in this study, the bandgap increases with an increasing lattice parameter. This phenomenon has good consistency with the experimental results.
The growth interfaces of CdMnTe（CMT） crystals grown by traveling heater method（THM） were studied. Two types of polycrystalline CMT feed ingots synthesized in a traditional rocking furnace and vertical Bridgman（VB） furnace were adopted in THM growth, and the effects of the polycrystalline feed on the growth interface were revealed. The morphology of the growth interface of CMT crystal（CMT2） grown from the feed by vertical Bridgman was smoother with lower curvature compared with that of CMT crystal（CMT1） from the feed by rocking furnace. The radial Mn composition and Te inclusion distribution of the CMT wafers were analyzed and correlated to the growth interface. The Mn segregation along the radial direction and Te inclusion density of CMT2 were lower than those of CMT1. The VB method synthesized polycrystalline feed could improve the growth interface morphology, which is beneficial for decreasing the Te inclusions and Mn segregation in CMT wafers.
