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中文摘要：
通过低温水热的合成方法合成了一例新的低温相GeO2晶体（l-GeO2）,并对其进行了红外光谱、热重以及X射线衍射的分析表征.晶体学测试结果表明,l-GeO2属于四方晶系,P4/mcc空间群,晶胞参数a=b=8.832（4）？,c=14.479（7）？,V=1129.4（9）？3,Z=4,R1=0.0629,wR2=0.1540.晶体结构中包含一个由4个双四元环单元（D4R）和4个GeO4四面体交替相连而形成的沿[001]方向的一维（1D）12-元环孔道.采用密度泛函理论下的第一性原理平面波超软赝势方法,对l-GeO2的电子结构和光学性质进行了理论计算.计算结果表明l-GeO2为直接带隙半导体,带宽为3.31 eV;其价带主要由O的2p电子构成,导带主要由Ge的4s和4p态电子构成;静态介电常数ε1（0）=1.92,折射率n（0）=1.24,吸收系数最大峰值为8.9×104 cm-1,最大反射率为12%.比较分析了l-GeO2与石英相GeO2（q-GeO2）和金红石相GeO2（r-GeO2）的复介电函数、复折射率、吸收谱以及反射谱等光学性质的异同点.结果显示l-GeO2的能带结构和光学性质与q-GeO2较接近,与r-GeO2的相差较大.
英文摘要：
A novel low temperature phase l-GeO2 crystal has been synthesized under hydrothermal condi-tions and characterized by means of IR spectrum,thermogravimetric（TG） analysis and X-ray diffraction.a=b=8.832（4） ？,c=14.479（7） ？,V=1129.4（9） ？3,Z=4,R1=0.0629,wR2=0.1540.The 1D 12-member ring channels along the 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 reflec-tivity 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.
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