A novel low temperature phase l-GeO₂ crystal has been synthesized under hydrothermal conditions and characterized by means of IR spectrum, thermogravimetric (TG) analysis and X-ray diffraction. a＝b＝8.832(4) Å, c＝14.479(7) Å, V＝1129.4(9) ų, Z＝4, R₁＝0.0629, wR₂＝0.1540. The 1D 12-member ring channels along the [001] direction are formed by the alternate linking of D4R units and GeO₄ tetrahedra in l-GeO₂. The electronic structure and optical response functions of l-GeO₂ were calculated by using a first-principle ultra-soft pseudo-potential approach of the plane wave based upon density functional theory (DFT). The results show that: l-GeO₂ is a direct semiconductor with a band gap of 3.31 eV. The density of state of l-GeO₂ is mainly composed of Ge 4s, 4p and O 2p with the static dielectric function ε₁(0) of 1.92, the refractive index n(0) of 1.24, the maximum absoption coefficient of 8.9×10⁴ cm^－1 and the maximum reflectivity of 12%. Moreover, the same and different points of dielectric functions, refractive index, absorption spectra and reflection spectra of l-GeO₂, q-GeO₂ and r-GeO₂ are compared. The results indicate that the band structures and optical properties of l-GeO₂ are similar to that of q-GeO₂ but much difference to that of r-GeO₂.

Key words: low temperature phase, electronic structure, optical property, the first-principle