First-principles study of the ferroelectric and optical properties of BaTeMo2O9

Electronic structure, spontaneous polarization and optical properties of single crystal BaTeMo2O9 have been investigated based on density-functional theory. It is found that BaTeMo2O9 has a direct-band-gap of 2.78 eV and there exists obvious hybridization between O 2p–Te 5p and O 2p–Mo 4d states. The results show that this compound is a good ferroelectric with large spontaneous polarization, which mainly arises from the strong Te–O and Mo–O hybridization. The interband contributions to the peaks of the optical spectra are discussed in details. Furthermore, the nonlinear optical properties are calculated by using 2n + 1 theorem applied to an electric-field dependent energy functional. The large NLO susceptibilities reveal that BaTeMo2O9 is a high-performance NLO crystal.

Research highlights
► As a multifunctional noncentrosymmetric compound, single crystal BaTeMo2O9 is not only a potential nonlinear optical crystal but also a good ferroelectric material.
► First, based on the Berry-phase approach, the obtained spontaneous polarization indicates that BaTeMo2O9 is a good ferroelectric.
► Second, combining with its electronic structure, we analyze the interband contributions to the peaks in the imaginary part of dielectric function.
► In addition, by adopting 2n + 1 theorem applied to an electric-field dependent energy functional, we perform the theoretical calculations of the nonlinear optical (NLO) susceptibilities of single crystal BaTeMo2O9, the large NLO susceptibilities reveal that BaTeMo2O9 is a high-performance NLO crystal.