We have computed second and third nonlinear optical susceptibilities of two crystalline bulk tellurium oxide polymorphs: α -TeO 2 (the most stable crystalline bulk phase) and γ -TeO 2 (the crystalline phase that ressembles the more to the glass phase). Third-order nonlinear susceptibilities of the crystalline phases are two orders of magnitude larger than α -SiO 2 cristoballite, thus extending the experimental observations on glasses to the case of crystalline compounds. While the electronic lone pairs of Te contribute to those large values, a full explanation of the anisotropy of the third-order susceptibility tensor requires a detailed analysis of the structure, in particular, the presence of helical chains, that seems to be linked to cooperative nonlocal polarizabilty effects
