Phase stability in ferroelectric bismuth titanate: a first-principles study.

Experimental data on the structure of ferroelectric oxide bismuth titanate suggest two different kinds of structures, i.e. orthorhombic and monoclinic. Density-functional-theory-based (DFT) first-principles calculations have been performed to determine the most stable structure of bismuth titanate among experimentally observed structures. Orthorhombic and monoclinic phases are optimized to zero pressure and lattice parameters were determined as a=5.4370, b=5.4260, c=32.6833 A and Z=4 for the structure with space group B2cb, and a=5.4289, b=5.4077, c=32.8762 A, beta=90.08 degrees and Z=4 for the structure with space group B1a1. Static and relaxation calculations show that the monoclinic structure with space group B1a1 is the most stable structure.