摘要
Methylammonium lead iodide,as related organometal halide perovskites,emerged recently as a particularly attractive material for photovoltaic applications.The origin of its appealing properties is sometimes assigned to its potential ferroelectric character,which remains however a topic of intense debate.Here,we rationalize from first-principles calculations how the spatial arrangement of methylammonium polar molecules is progressively constrained by the subtle interplay between their tendency to bond with the inorganic framework and the appearance of iodine octahedra rotations inherent to the perovskite structure.The disordered tetragonal phase observed at room temperature is paraelectric.We show that it should a priori become ferroelectric but that iodine octahedra rotations drive the system toward an antipolar orthorhombic ground state,making it a missed ferroelectric.
基金
W.-Y.T.acknowledges the support from F.R.S.-FNRS Belgium.J.-Z.Z.acknowledges the support from the Startup Funding for Outstanding Young Scientist of South China Normal University and the financial support of China Scholarship Council(Grant No.202006755025)
The authors acknowledge access to the CECI supercomputer facilities funded by the F.R.S-FNRS(Grant No.2.5020.1)
the Tier-1 supercomputer of the Federation Wallonie-Bruxelles funded by the Walloon Region(Grant No.1117545).
