  The Z-scan measurements for the non-centrosymmetric optical crystals
{\beta}-BaTeMo2O9 (BTMO) were performed. The corresponding experiments were
carried out using the 5 ns pulses of the second harmonic of a nanosecond Nd:YAG
laser at the 532 nm wavelength. It was shown that the studied crystals possess
promising third-order optical susceptibilities, which allow to use the crystal
as optical limiters. The comparison with other oxide materials is presented. To
clarify the origin of the observed effect, the electronic and optical
properties of BTMO were calculated using the density functional theory
(DFT)-based method. The performed calculations of the electronic and optical
properties revealed certain peculiar features that can be suitable for the
non-linear optical applications. The relation between the observed nonlinear
optical features and the calculated band structure is emphasized. The values of
the calculated band gap and refractive index for {\beta}-BaTeMo2O9 are also
reported.
